River Hill Contracting Pty Ltd v Moore - [2022] WADC 60

JURISDICTION : DISTRICT COURT OF WESTERN AUSTRALIA
IN CIVIL

LOCATION:   PERTH
CITATION:   RIVER HILL CONTRACTING PTY LTD -v- MOORE [2022] WADC 60
CORAM:   COMMISSIONER COLLINS
HEARD:   11 MARCH 2022 AND WRITTEN SUBMISSIONS 25 FEBRUARY, 9, 10, 14 & 18 MARCH 2022
DELIVERED          :   28 JUNE 2022
FILE NO/S:   APP 80 of 2021
BETWEEN:   RIVER HILL CONTRACTING PTY LTD
Appellant
AND
COLIN MOORE
Respondent

ON APPEAL FROM:
Jurisdiction              :   WORKCOVER WA
Coram:   ARBITRATOR NUNN
File Number            :   A96333

Catchwords:

Workers' compensation - Appeal from arbitration - Whether arbitrator made an error of law in failing to apply cause of action estoppel or Anshun estoppel involving a claim under the Workers' Compensation and Injury Management Act 1981

Legislation:

Workers' Compensation and Injury Management Act 1981 (WA)

Result:

Leave to appeal granted, but appeal dismissed

Representation:

Counsel:

Appellant	:	Mr J J Sheldrick
Respondent	:	Mr J N Trigg

Solicitors:

Appellant	:	Hall & Wilcox (Perth)
Respondent	:	Hoffmans Lawyers

Case(s) referred to in decision(s):

Australian Broadcasting Tribunal v Bond (1990) 170 CLR 321
Beasley v Pilbara Mining Alliance Pty Ltd [2022] WASCA 25
BHP Billiton Iron Ore Pty Ltd v Brady [2008] WASCA 250
Catholic Education Office of WA v Granitto [2012] WASCA 266
Clayton v Bant [2020] HCA 44
Department of Education v Kenworthy (1990) 3 WAR 1
DP World Australia Ltd v Fremantle Port Authority [2009] WASCA 16
Henderson v Henderson (1843) 3 Hare 100; [1843-60] All ER Rep 378; (1843) 67 ER 313
House v The King (1936) 55 CLR 499
Kuligowski v Metrobus (2004) 220 CLR 363
Pacific Industrial Co v Jakovljevic [2008] WASCA 60
Port of Melbourne Authority v Anshun Pty Ltd (1981) 147 CLR 589
Regis Aged Care Pty Ltd v Hunter [2018] WASCA 50
Salmon Street Ltd (In Liquidation) formerly General Motors‑Holden's Limited v Jorgensen (1992) 56 SASR 158
Sotico Pty Ltd v Wilson [2007] WASCA 112
Taylor v Star Broken Meats (Unreported, WASCA, Library No 920434, 26 August 1992)
The Cerebral Palsy Association of Western Australia Ltd t/as Ability Centre v Papalia [2019] WADC 180
Tomlinson v Ramsey Food Processing Pty Ltd [2015] HCA 28; (2015) 256 CLR 507
Trawl Industries of Australia Pty Limited (in liquidation) v Effem Foots Pty Ltd (1992) 36 FCR 406
UBS AG v Tyne [2018] HCA 45
Woolworths Ltd v Director of Liquor Licensing [2013] WASCA 227
Zetta Jet Pte Ltd v The Ship 'Dragon Pearl' (No 2) [2018] FCAFC 132

COMMISSIONER COLLINS:

A. Introduction

This appeal concerns two arbitrations brought under the Workers' Compensation and Injury Management Act 1981 (WA) (Act).
The first arbitration concerns the decision of Arbitrator Rutherford (Rutherford Arbitration and/or Rutherford Decision). That decision is also referred to as A56736. In that arbitration, the claimant, Colin Moore (Mr Moore), sought weekly compensation payments for an injury that occurred on 5 May 2017. Arbitrator Rutherford ultimately dismissed Mr Moore's application, with reasons given on 16 March 2020.
The second arbitration concerns the decision of Arbitrator Nunn (Nunn Arbitration and/or Nunn Decision). That arbitration remains on foot and is yet to be determined: it is also referred to as A96333. In that arbitration, Mr Moore again sought weekly compensation payments for an injury that occurred on 5 May 2017. However, before the substantive matter was heard, a preliminary issue was raised as to whether Mr Moore was estopped from proceeding with the dispute because of either cause of action estoppel or Anshun estoppel. Arbitrator Nunn heard that application and determined that Mr Moore's application was not barred by either of those estoppels. That decision was handed down on 21 October 2021. In effect, Arbitrator Nunn dismissed the application (preliminary issue), leaving Mr Moore to pursue his claim.
The respondent to the Nunn Arbitration, River Hill Contracting Pty Ltd (River Hill), has appealed the Nunn Decision under s 247(1) of the Act. River Hill filed an amended notice of appeal on 23 November 2021. River Hill and Mr Moore filed outlines of written submissions on 25 February and 9 March 2022 respectively. River Hill filed additional materials on 10 March 2022.
I heard River Hill's appeal on 11 March 2022. At the conclusion of the hearing, I invited the parties to submit a list of authorities dealing with estoppel and interstate workers' compensation matters. The parties filed a list of authorities on 18 March 2022. Separately to this, River Hill filed additional materials on 14 March 2022 to correct some of its submissions.
For the reasons that follow, I grant leave for River Hill to bring the appeal, but ultimately dismiss the appeal.

B. Background to the Rutherford Arbitration

The appeal hearing was conducted against the background as set out in the Rutherford Arbitration and the Rutherford Decision. That background can be summarised as follows.
River Hill employed Mr Moore as a plant operator/truck driver.
On 5 May 2017, Mr Moore suffered a back injury when he was hit by a load bucket which crushed him against a hopper.
On 29 May 2017, Mr Moore made a claim for compensation under the provisions of the Act. The claim form signed by Mr Moore asked him to identify his 'most serious injury', to which he wrote 'L2 L3 fractures' (being a reference to fractures of Mr Moore's L2/L3 spine). The date of the injury specified in the form was 5 May 2017. In response to the question, 'what action was involved', Mr Moore wrote 'hopper leg shifted crushing me between hopper & bucket'.
On or about 7 June 2017, Allianz Australia Insurance Limited (Allianz), River Hill's insurer, accepted liability for Mr Moore's claim. Allianz's Noel Catchpole, WC Claims Manager for WA, WA Workers' Compensation, wrote to River Hill and Mr Moore by a document bearing the date 7 June 2017 and the following description:
Form 3A
Workers' Compensation and Injury Management Act 1981
(Section 57A(3)(a))
INSURER'S NOTICE THAT LIABILITY IS ACCEPTED
The Form 3A contained the following additional information:
Date of injury by accident or approximate date of onset of condition: 05/05/2017
Nature of incapacity: lower back fractures in L2 and L3
Date claim made by employer: 01/06/2017
In respect of the above claim you are notified that liability is accepted in respect of weekly payments claimed by the worker.
Weekly payments of compensation commenced shortly thereafter.
Following his injury and after being certified unfit for work for a number of months, Mr Moore commenced a return-to-work program in consultation with both his rehabilitation provider and Dr Coert Erasmus, his general practitioner (GP).
On 23 October 2017, Mr Moore's GP certified that Mr Moore had full capacity for work from 24 October 2017.
On 25 October 2017, River Hill ceased weekly payments of compensation to Mr Moore on the basis that he had returned to work.
Mr Moore's evidence was to the effect that he had received weekly compensation payments from 17 May to 24 October 2017 and that he did not consent to the cessation of those payments. Nor did he receive notice from Allianz informing him of its intention to cease his weekly payments.
Ultimately, the parties were not able to resolve their dispute by agreement and so the matter proceeded to arbitration.
On 6 and 7 June 2019, Arbitrator Rutherford heard Mr Moore's application for compensation under the Act.
In the Rutherford Arbitration, Mr Moore did not accept that he had returned to work. He contended that River Hill had unlawfully discontinued his payments. He sought an order under s 61(3) of the Act to reinstate his weekly compensation payments from 25 October 2017, being the date River Hill ceased payments.
In the alternative, Mr Moore sought orders recommencing his weekly compensation payments for total incapacity from 1 July 2018 under s 62 of the Act. This was on the basis that he was then, and continued to be at the time of the Rutherford Arbitration, totally incapacitated for work. In this part of Mr Moore's application, he submitted that the L4/L5 area of his lower back was also damaged during the work accident in May 2017. He also claimed that he had developed a psychological condition because of his back injuries.
River Hill disputed whether Mr Moore was incapacitated as a result of the work injury and submitted that it was not liable to pay Mr Moore compensation under s 62 of the Act. It also submitted that Mr Moore had not claimed for the other alleged injuries/conditions and that they had not been previously admitted, or determined. In the circumstances, any injury other than the admitted L2/L3 fracture injury could not be considered in the context of Mr Moore's s 62 application.
Arbitrator Rutherford determined that there were broadly two issues to be resolved. First, whether River Hill (and its insurer) had unlawfully discontinued weekly payments of compensation to Mr Moore on about 25 October 2017 in breach of s 61 of the Act. If payments had been unlawfully terminated, whether an order should be made recommencing weekly payments, considered in light of whether Mr Moore was incapacitated. Secondly, if the weekly payments had not been unlawfully discontinued, did the evidence establish that Mr Moore was totally incapacitated from 1 July 2018 as a result of the injury such that payments of compensation for total incapacity should re‑commence from 1 July 2018 under s 62 of the Act.
On 16 March 2020, Arbitrator Rutherford dismissed Mr Moore's application and published his reasons. As to the s 61 application, Arbitrator Rutherford found that Mr Moore had returned to work. Accordingly, River Hill's cessation of weekly payments of compensation was not unlawful. In the circumstances, Arbitrator Rutherford held that Mr Moore had not established that River Hill had unlawfully terminated his weekly compensation payments.
As to the s 62 application, Arbitrator Rutherford found that Mr Moore had not established that he was incapacitated from 1 July 2018 as a result of the admitted injury. In this regard, the admitted injury involved the L2/L3 fracture of Mr Moore's lower back and not the L4/L5 area of Mr Moore's lower back, because Mr Moore had not made a claim regarding that injury and nor had River Hill admitted that injury. In effect, any remedy Mr Moore had under s 62 turned on River Hill's admission of liability for an injury to his L2/L3 spine only.
I observe here that it was common ground at the hearing of the appeal that Mr Moore did not appeal the Rutherford Decision. Neither party suggested otherwise.

C. The Nunn Arbitration

C.1 Background - overview

Before Arbitrator Nunn, River Hill sought, in effect, to prevent Mr Moore, by the law of estoppel, from re-litigating what it saw as the same action again.
The relevant facts in the Nunn Arbitration can be summarised as follows.
On 6 April 2020, Mr Moore completed a claim form in relation to compensation under the provisions of the Act. In his claim form, Mr Moore stated that his 'most serious injury' was an injury he described as 'L4/L5 injury, L5/S1 injury, psychological injury'. The date of the injury specified in the form was 5 May 2017. Arbitrator Nunn noted that Mr Moore's claim was based on his first medical certificate, being the same medical certificate that he had relied upon in respect of his injuries to L2/L3 and for which River Hill had admitted liability.
By a document headed Form 3C and bearing the date 12 June 2020, Allianz's Mr Catchpole wrote to River Hill and Mr Moore. The Form 3C contained the following heading:
Form 3C
Workers' Compensation and Injury Management Act 1981
(Section 57A(3)(c))
INSURER'S NOTICE WHERE NO DECISION ABOUT LIABILITY
The Form 3C contained the following additional information:
Date of injury by accident or approximate date of onset of condition: 05/05/2017
Nature of incapacity: lower back injury & psychological injury - crushed between hopper and loader bucket
Date claim made by employer: 10/06/2020
In respect of the above claim you are notified that a decision as to whether or not liability is to be accepted in respect of weekly payments claimed by the worker is not able to be made within the time allowed by section 57A(3) of the Act.
The reasons why the decision is not able to be made are as follows:
Allianz requires further information as to the nature and extent of any injury(s) as claimed and whether the injury arose in the course of the claimant's employment and if the claim is in breach of s 178(1)(b).
Arbitrator Nunn noted that although River Hill had not denied liability, a dispute for the purposes of the Act had arisen.
On 6 May 2021, Arbitrator Nunn heard a preliminary application in relation to Mr Moore's L4/L5 injury. River Hill submitted that Mr Moore was estopped from proceeding further with his application because of either cause of action estoppel or Anshun estoppel. River Hill submitted that that was the effect of the dispute and the decision in the Rutherford Arbitration. River Hill also submitted that Mr Moore's claim was not maintainable under s 178 of the Act.
Arbitrator Nunn outlined the issues for determination as follows:
11. River Hill contends that the effect of the dispute and decision in A56736 is that Mr Moore is estopped from proceeding further with this present dispute on the basis of either cause of action estoppel or Anshun estoppel.
12. Furthermore, River Hill contends that Mr Moore's claim is also not maintainable pursuant to the prescriptions of s 178.
On 21 October 2021, Arbitrator Nunn determined that:
13. For the following reasons I am unable to agree that any of the arguments advanced by River Hill bar Mr Moore from proceeding further with his claim.
In effect, Arbitrator Nunn dismissed River Hill's preliminary application with the result that Mr Moore could litigate the substantive matters in the Nunn Arbitration.

C.2 What was in issue before Arbitrator Rutherford?

In the context of River Hill's estoppel arguments, Arbitrator Nunn summarised the issue before Arbitrator Rutherford in the following terms:
24.For present purposes only the s 62 dispute in A56736 is relevant. I have not considered the return to work / s 61(3) dispute that was before Arbitrator Rutherford.
Arbitrator Nunn identified the critical passages that Arbitrator Rutherford relied upon as follows:
30. The critical passages of the arbitrator's decision lie between [117] and [145]. Having regard to these paragraphs reveals that the following comments and findings were central to the arbitrator's decision.
(a) The only injury which had been claimed was the L2/L3 injury.
(b) An application under s 58 is a different enquiry to that required by s 62.
(c) A review under s 62 cannot include any injuries other than those that have been accepted or determined. Section 62 is confined to situations where the liability to make the weekly payments had been either admitted or determined. There having been no claim nor admission in respect of the L4/L5 injuries these could not be included within Mr Moore's s 62 dispute.
(d) The L4/L5 injury could not be considered within the scope of the s 62 as it was not asserted as being a consequential injury but rather as an original injury for which no claim had been made.
(e) Any claim for the L4/L5 injuries is subject to other procedural and jurisdictional matters such as questions of prejudice under s 178 and whether a valid claim has in fact been made under s 57A. To consider this within the scope of a s 62 dispute would be to ignore these requirements.
(f) As Mr Moore contended that the L4/L5 injuries were aggravations of a pre-existing disease such limb of injury could not be established without consideration of s 5(5) factors of which there was no evidence.
31.It is clear that the arbitrator agreed with River Hill's arguments that as a matter of the proper application of the Act (and indeed quite possibly as a matter of jurisdiction given there had been no claim made in respect of the L4/L5 injury) the only injury that could be considered within the scope of Mr Moore's s 62 application was the admitted L2/L3 injury.
32. The arbitrator went on to find that Mr Moore had in fact been incapacitated (in the sense that he had been unable to compete for work in a market reasonably open to him) however this was not as a result of the admitted L2/L3 injury. Although not strictly necessary for him to have done so the arbitrator went on to find that this was a result of the L4/L5 condition. As this was beyond the scope of the dispute before him (as liability for the L4/L5 injury had neither been admitted nor determined) Mr Moore was not entitled to the weekly payments he sought.
33. Whether I agree with the arbitrator or not is irrelevant. I exercise no appeal or review powers in respect of A56736 nor am I bound by that decision. What is relevant for the current dispute is to ascertain what was in dispute between the parties in A56736, what the arbitrator in fact determined and his reason for doing so and to then compare that to the present proceedings.

C.3 Cause of action estoppel

After setting out the relevant authorities, Arbitrator Nunn summarised the parties' respective arguments in the Rutherford Arbitration as set out below, and then made findings as to liability:
39. River Hill contend that when the two disputes are compared it is apparent that:
(a)The series of facts Mr Moore must allege and prove to substantiate his right to judgement are identical.
(b)The legal right alleged to have been infringed is the same in both cases, namely an ongoing right to weekly payments of compensation.
(c)The same evidence is required to prove Mr Moore's case (as to incapacity) in both cases;
(d)The rights claimed are of substantially equivalent nature and cover the same subject matter (i.e. incapacity)
40. I agree that the remedy sought in both disputes is the same and that similar (if not identical) evidence has been relied on in regards of the question of incapacity.
41. However, whether Mr Moore is entitled to such compensation is consequent upon a determination that he has in fact suffered the compensable injury said to give rise to that incapacity.
42. In the present dispute the matter to be principally litigated is whether Mr Moore has a maintainable claim in respect of the L4/L5 injury and whether, if he does, that injury is in fact an injury under the Act, that is, whether it is compensable.
43. This issue was never in fact litigated in A56736 as it was determined that only those injuries that had been accepted or determined as being compensable could be included within the scope of the s 62 dispute brought by Mr Moore.
44. As pointed out by River Hill, evidence and questions of fact necessary to the determination of whether the L4/L5 injury fell within limb 'd' of the definition of injury had not been led by Mr Moore (being the s 5(5) factors). Indeed, as it was also pointed out by River Hill, no valid claim had in fact been made in respect of the L4/L5 injures.
45. Accordingly, by River Hill's own submissions in A56736 the evidence Mr Moore requires to succeed in respect of his claim in this dispute was not led in A56736 and has not been considered on the merits by an arbitrator.
46. In my view, this is a situation akin to that addressed by Justice Pullin in Willoughby [No 2] where the substantive issue was never litigated on the merits (or indeed heard at all).
47. Furthermore, in my view, the right infringed is not the right to compensation, but rather the right to agitate for compensation if liability for an injury is not admitted. That is the process provided for by s 57A and s 58.
48. The question of whether Mr Moore has a valid claim and/or a compensable injury in respect of the L4/L5 injury has never been determined. The arbitrator decided that this could not in fact be determined in A56736. As the arbitrator noted, the inquiry under s 62 is a very different one than that required by s 58.
49. Accordingly, although the arbitrator's decision was final in respect of the s 62 issue and all matters encompassed by that dispute no final decision in regard to the issue of whether Mr Moore has a valid and maintainable claim or in fact suffered a compensable injury to his back at L4/L5 has been determined on its merits.
50. Accordingly, I do not consider that this is a situation akin to the cases River Hill contend are 'on all fours' with this situation such as Sahin v National Bank Limited[2012] VSCA 317, Trawl Industries of Australia Pty Limited (in liquidation) v Effem Foods Pty Limited(1992) 36 FCR 406 or Zavodnyik v Alex Constructions Pty Ltd(2005) 67 NSWLR 457.
51. As noted above, I accept that the question of incapacity was determined between the parties. However, that is a separate question to whether the aggravation of Mr Moore's L4/L5 condition is a compensable injury. I also note that the question of incapacity is a separate question from whether Mr Moore might be entitled to some other form of compensation (such as statutory or medical expenses) in respect of his L4/L5 injury. Such an entitlement would necessarily require determination of whether Mr Moore had suffered a compensable injury.
52.The arbitrator's determination that Mr Moore was incapacitated as a result of his L4/L5 condition (as opposed to the L2/L3 injury River Hill admitted liability for) may give rise to some other forms of estoppel such that the parties may be barred from disavowing something contrary to the facts as to incapacity determined by Arbitrator Rutherford. However, that is not an issue presently before me and I express no concluded view on this issue.
53. On the facts of this matter I am not persuaded that cause of action estoppel properly applies or that the arbitrator's pronouncements in regards to Mr Moore's incapacity serve to estop Mr Moore from having the question of his present claim (and whether he has suffered a compensable injury at L4/L5) determined.
54. In my view, Mr Moore's present application is not estopped by cause of action estoppel.

As may be observed, Arbitrator Nunn referred to the only injury that had been claimed in the Rutherford Arbitration, which was the L2/L3 injury: [30(a)]. By contrast, Arbitrator Nunn found that the central issue in the dispute before him was whether Mr Moore had a maintainable claim in respect of his L4/L5 injury and if so, whether that injury was compensable under the Act: [42]. Arbitrator Nunn found at [43] that Mr Moore's L4/L5 injury was 'never in fact litigated' in the Rutherford Arbitration and had 'never been determined': [48]. That was because Arbitrator Rutherford determined that only those injuries that had been accepted or determined as being compensable could be included within the scope of the s 62 dispute brought by Mr Moore. That reasoning, in turn, relied on the differences between s 58 and s 62 of the Act and the functions they serve under the Act.
Another matter that may be observed is that in the Rutherford Arbitration, River Hill argued that Mr Moore had not made a valid claim in respect of his L4/L5 injuries: [44]. And further, River Hill submitted that the evidence that Mr Moore needed in order to succeed in respect of his claim had not been led: [45]. Put differently, River Hill's principal arguments before Arbitrator Rutherford were to the effect that Mr Moore had not made a valid claim in respect of his L4/L5 injuries and that Arbitrator Rutherford should not consider that claim for the purposes of s 62 of the Act. River Hill was ultimately successful in persuading Arbitrator Rutherford as to the merits of its argument.
River Hill's position in the Rutherford Arbitration can be contrasted with the position it took in the Nunn Arbitration. Relevantly, River Hill sought to argue in the Nunn Arbitration that the effect of the Rutherford Decision was to estop Mr Moore from proceeding further with his L4/L5 injury application by reason of either cause of action estoppel or Anshun estoppel. River Hill contended that it was effectively being asked to litigate the same cause of action twice when that issue (the question of weekly payments of compensation) was finally determined in the Rutherford Arbitration: [36]. It did not matter that the Rutherford Arbitration concerned s 62 of the Act whereas the Nunn Arbitration concerned s 58 of the Act. The evidence and remedy sought were substantially the same: [35].
As may be observed, River Hill contended in the Nunn Arbitration and this appeal that the Rutherford Decision dealt with all of Mr Moore's claims for weekly payments of compensation, irrespective of whether they were made under s 58 or s 62 of the Act. At the same time, River Hill submitted to Arbitrator Rutherford that he could not hear Mr Moore's claim in respect of his L4/L5 injuries because that claim was not a valid claim for the purposes of s 62 of the Act, with which Arbitrator Rutherford agreed. It seems to me that implicit in River Hill's argument before Arbitrator Rutherford is the recognition that there are fundamental differences between the operation and function of s 58 and s 62 of the Act. Given this, River Hill's submissions in the Nunn Arbitration and on appeal are not easily reconciled.

C.4 Anshun estoppel

In the alternative to cause of action estoppel, River Hill submitted that Mr Moore was estopped from bringing his claim in the Nunn Arbitration on the basis of Anshun estoppel: A96333 was so connected with A56736, that it would be unreasonable for Mr Moore to bring the subsequent action: [55].
After setting out the relevant authorities, Arbitrator Nunn summarised the parties' respective arguments as follows:
60. The present dispute is brought pursuant to s 58(1). Section 58(1) is predicated on the circumstances mentioned in s 57A existing.
61. In my opinion, this is the determinative factor in considering whether Anshun estoppel applies in this situation.
62. In A56736 the circumstances in s 57A in regard to the claimed injury did not exist. No claim in respect of the L4/L5 injury yet existed.
63. The essence of River Hill's argument is that that claim (i.e. as contemplated by s 178 of the Act) should have been brought at the same time as the issues in A56736 were litigated and it was in fact unreasonable not to have done so such that Mr Moore should now be estopped from agitating for determination in respect of that claim that has now been brought.
64. I would agree with River Hill that Anshun estoppel might operate had Mr Moore in fact brought a claim (as contemplated by s 178) such that the cause of action established by s 57A and 58(1) was open to him but where he had not pursued that in A57636.
65. However, those are not the facts of this case. No dispute under s 58 could have been brought under A57636 as no claim had been made. Indeed, the same reasoning was applied to the application of s 62 in A57636.
66. In my view, Anshun estoppel applies to the various causes of actions and legal arguments that a party might (and should) raise so all issues in dispute can be finally dealt with together.
67. Given the lack of a claim no legal argument could have arisen in regard to liability for the L4/L5 injury under s 58 at that time.
68. In my view, River Hill contend that Mr Moore should have brought his claim so it could be litigated with the other issues in A57636. However, it is not for the employer to dictate when a claim for injury must be brought by a worker. The Act prescribes that it should be brought within 12 months of the date of injury and s 178 provides the employer a mechanism to bar the progress of that claim if it is not brought within that time. Indeed, River Hill have contended that Mr Moore is barred on that basis as well.
69. If Mr Moore is allowed to proceed will this invite the possibility of an inconsistent judgement?
70. Although it might allow for a different outcome in that Mr Moore may secure the compensation he seeks I cannot see that such an outcome would be necessarily inconsistent with the decision in A57636.
71. That decision turned on whether the L4/L5 injury could be encompassed within the s 62 dispute. It could not. Strictly speaking it was neither necessary nor central to the arbitrator's decision in A57636 to determine anything further in respect of the L4/L5 injury, only that Mr Moore did not suffer any incapacity as a result of the admitted L2/L3 injury.
72. In any event, were Mr Moore to succeed in establishing he had a compensable injury at L4/L5 that gave rise to an incapacity that would not necessarily be inconsistent with A57636 which was dismissed on the basis that any incapacity Mr Moore had did not result from the L2/L3 injury.
73. For these reasons Mr Moore is not estopped from proceeding with the present dispute by reason of Anshun estoppel.
It may be seen that Arbitrator Nunn's reasoning for finding that Anshun estoppel had no application involved several strands.
First, the dispute before Arbitrator Nunn involved the application of s 58 of the Act, which Arbitrator Nunn found was predicated on the circumstances mentioned in s 57A existing: [60]. By contrast, in the Rutherford Decision, the circumstances in s 57A did not exist as no claim in respect of Mr Moore's L4/L5 injury had been made: [62].
Secondly, and perhaps most importantly, Arbitrator Nunn found that no dispute under s 58 could have been brought in the Rutherford Arbitration as Mr Moore had not made a claim in respect of his L4/L5 injury: [65]. In effect, in the absence of a claim, it was not possible in the Rutherford Arbitration to conduct legal argument about Mr Moore's entitlement to compensation in respect of his L4/L5 injury (if any).
Thirdly, Arbitrator Nunn noted that River Hill argued that Mr Moore should have brought a claim at the same time as litigating A56736 and that it was unreasonable not to have done so: [63], [68]. In response to this argument, Arbitrator Nunn noted that under the Act, a worker has 12 months from the date of injury in which to make a claim: the Act does not otherwise prescribe when a claim should be made: [68].
The thrust of Arbitrator's Nunn's reasoning at [68] is that the Act manifests an intention that claims for injuries arising from the same event may be made at different intervals or points in time provided they comply with the time limits under the Act.

D. River Hill relied on two grounds of appeal and two questions of law in this appeal

In its amended notice of appeal, River Hill identified two questions of law, namely:
1.Whether the Arbitrator committed an error of mixed fact and law in finding (at [54]) that Mr Moore was not estopped in A96333 by cause of action estoppel due to the earlier decision in A56736, by:
(a)acting contrary to the principle of cause of action estoppel that it is:
(i)not necessary that the source of the rights asserted are identical; and
(ii)sufficient that they be substantially equivalent and cover substantially the same subject matter; and
(b)finding (at [39(c)] and [39(d)]) that River Hill's submissions were limited to the question of incapacity.

2.Whether the Arbitrator committed an error of mixed fact and law in finding (at [73]) that Mr Moore was not estopped by reason of Anshun estoppel, by:
(a)acting contrary to the Anshun principle that it would be unreasonable not to plead an alternative claim if, having regard to the nature of the claim and its subject matter, it would be expected that the party would raise the claim and thereby enable the relevant issues to be determined in the one proceeding; and
(b)finding (at [68]) that it is not for the employer to dictate when a claim for injury must be brought by a worker.

River Hill's amended notice of appeal included the following two grounds of appeal, namely:
1 For the reasons set out in the particulars below, the Arbitrator committed an error of mixed fact and law in finding (at [54]) that the respondent was not estopped in A96333 by cause of action estoppel due to the earlier decision in A56736 and should have found to the contrary.
Particulars
(a)The Arbitrator found that:
(i)A56736 was a ‘s 62 dispute' (at [43]);
(ii)A96333 was brought under s 58 (at [47] and [48]);
(iii)it had not been determined whether the respondent had a compensable injury in respect of the L4/L5 injury (at [48] and [49]); and
(iv)hence, cause of action estoppel did not apply.
(b)In so finding, the Arbitrator acted contrary to the principle of cause of action estoppel that it is:
(i)not necessary that the source of the rights asserted are identical; and
(ii)sufficient that they be substantially equivalent and cover substantially the same subject matter.
(c)In properly applying that principle, the Arbitrator should have found that the causes of action were the same because the respondent sought the same relief or remedy (being weekly payments of compensation from 1 July 2018) for the same body part, being the lower back, and the same accident on 5 May 2017 and that the rights are of substantially equivalent nature and cover substantially the same subject matter.
(d)The choice made by the respondent to not rely upon the s 58 gateway as an alternative to the s 62 gateway in A56736 should not have been found by the arbitrator to preclude the operation of cause of action estoppel.
(e)The Arbitrator erred in fact in finding (at [39](c)) and (d)) that the appellant's submissions were limited to the question of incapacity.
2 For the reasons set out in the particulars below, the Arbitrator committed an error of mixed fact and law in finding (at [73]) that the respondent was not estopped by reason of Anshun estoppel and should have found to the contrary.
Particulars
(a)The Arbitrator found (at [67]) that, given a claim for the L4/L5 injury had not been made, no legal argument could have arisen in regard to liability for the L4/5 injury under section 58 at the time of A56736 and hence Anshun estoppel did not apply.
(b)In so finding, the Arbitrator acted contrary to the Anshun principle that it would be unreasonable not to plead an alternative claim if, having regard to the nature of the claim and its subject matter, it would be expected that the party would raise the claim and thereby enable the relevant issues to be determined in the one proceeding.
(c)The Arbitrator should have found that, if it was considered necessary for the respondent to have submitted a claim form in order to bring an application under s 58 for the L4/5 injury, then the respondent should have done that prior to the hearing in A57636.
(d)In finding (at [68]) that it is not for the employer to dictate when a claim for injury must be brought by a worker, the Arbitrator erred in fact and in law in that:
(i) the appellant made no such submission (whether expressly or implicitly);
(ii)whether the appellant was seeking to dictate this to the respondent was irrelevant to the proper application of the Anshun principles; and
(iii)the proper application of principle should have led the Arbitrator to determine that the respondent, acting reasonably, should have taken whatever steps were required to include the L4/5 injury in A56736.
(e)The Arbitrator should have found that the subject matter was so closely connected with the section 62 claim in A56736 that it ought to have been raised.
I will refer to River Hill's first ground as cause of action estoppel and the second ground as Anshun estoppel.
Each of these grounds is addressed below.

E. Leave to appeal

Under s 247 of the Act, River Hill requires leave to appeal. Section 247(2) identifies the circumstances in which leave may be granted. As an amount of compensation has yet to be determined, I do not consider s 247(2)(a) has any application. Instead, I consider that s 247(2)(b) applies. In effect, I should not grant River Hill leave unless this appeal involves a question of law.
An appeal will involve a question of law if the Arbitrator has made an error of law or an error of mixed law and fact: BHP Billiton Iron Ore Pty Ltd v Brady [2008] WASCA 250 (BHP Billiton) [3]. Further, an administrative tribunal or body will make an error of law in deciding a matter if, at least in the absence of a contrary intention in the statute which established it, it identifies a wrong issue or asks itself a wrong question: Woolworths Ltd v Director of Liquor Licensing [2013] WASCA 227 [65]. A decision does not involve an error of law unless the error is material to the decision in the sense that it contributes to it so that, but for the error, the decision would have been, or might have been, different: Australian Broadcasting Tribunal v Bond (1990) 170 CLR 321, 353 (Australian Broadcasting Tribunal); BHP Billiton [15].
In my view, this appeal involves a question of law. The parties' counsel did not dispute that the appeal involved a question of law (ts 3, ts 4). I therefore find that the preconditions for leave have been made out and I grant leave accordingly.
There was no suggestion that the notice of appeal was filed out of time or otherwise invalid.

F. Nature of appeal

An appeal under s 247 is to be conducted by way of review of the decision appealed against: s 247(5). Ordinarily, the appeal is conducted on the materials, which were before the arbitrator: s 247(6). The appeal is not a hearing de novo: Pacific Industrial Co v Jakovljevic [2008] WASCA 60 [20] (Pacific Industrial). If the court is satisfied that the appeal involves a question of law, then the court must conduct a real review of the arbitrator's decision: Sotico Pty Ltd v Wilson [2007] WASCA 112 [46] (Pullin JA); Pacific Industrial [20]; Catholic Education Office of WA v Granitto [2012] WASCA 266 [56] (Catholic Education Office).
For the purposes of the review, River Hill must provide a proper basis for disturbing the arbitrator's decision by pointing to some error in it. It is not sufficient for River Hill to simply invite the court to ignore the arbitrator's decision and substitute the court's decision for that of the arbitrator: Catholic Education Office [57]. The review must persuade the court that the order being reviewed should be varied, discharged or otherwise disturbed: Pacific Industrial [20], [26]; The Cerebral Palsy Association of Western Australia Ltd t/as Ability Centre v Papalia [2019] WADC 180 [12].

G. Estoppel - legal principles

In Tomlinson v Ramsey Food Processing Pty Ltd [2015] HCA 28; (2015) 256 CLR 507 (Tomlinson), French CJ, Bell, Gageler and Keane JJ stated that:
21Estoppel in relation to judicial determinations is of a different nature. It is a common law doctrine informed, in its relevant application, by similar considerations of finality and fairness. Yet its operation is not confined to an exercise of judicial power; it also operates in the context of a final judgment having been rendered in other adversarial proceedings. It operates in such a context as estoppel operates in other contexts: as a rule of law, to preclude the assertion of a right or obligation or the raising of an issue of fact or law.
22Three forms of estoppel have now been recognised by the common law of Australia as having the potential to result from the rendering of a final judgment in an adversarial proceeding. The first is sometimes referred to as 'cause of action estoppel'. Estoppel in that form operates to preclude assertion in a subsequent proceeding of a claim to a right or obligation which was asserted in the proceeding and which was determined by the judgment. It is largely redundant where the final judgment was rendered in the exercise of judicial power, and where res judicata in the strict sense therefore applies to result in the merger of the right or obligation in the judgment. The second form of estoppel is almost always now referred to as 'issue estoppel'. Estoppel in that form operates to preclude the raising in a subsequent proceeding of an ultimate issue of fact or law which was necessarily resolved as a step in reaching the determination made in the judgment. The classic expression of the primary consequence of its operation is that a 'judicial determination directly involving an issue of fact or of law disposes once for all of the issue, so that it cannot afterwards be raised between the same parties or their privies'. The third form of estoppel is now most often referred to as 'Anshun estoppel', although it is still sometimes referred to as the 'extended principle' in Henderson v Henderson. That third form of estoppel is an extension of the first and of the second. Estoppel in that extended form operates to preclude the assertion of a claim, or the raising of an issue of fact or law, if that claim or issue was so connected with the subject matter of the first proceeding as to have made it unreasonable in the context of that first proceeding for the claim not to have been made or the issue not to have been raised in that proceeding. The extended form has been treated in Australia as a 'true estoppel' and not as a form of res judicata in the strict sense. Considerations similar to those which underpin this form of estoppel may support a preclusive abuse of process argument.
(references omitted)
In Clayton v Bant [2020] HCA 44 (Clayton), Kiefel CJ, Bell and Gageler JJ stated that:
28Two forms of estoppel are potentially applicable. One is that sometimes referred to as 'cause of action' estoppel. The terminology has been recognised as problematic given the range of senses in which the expression 'cause of action' tends to be used. The relevant sense is that of title to the legal right established or claimed. Especially in a statutory context such as the present, the form of estoppel would be better referred to by the more generic description of 'claim' estoppel. The other form of estoppel is most commonly referred to in Australia as 'Anshun estoppel', after Anshun, although the Full Court chose to refer to it as the 'Henderson extension'.
29Both of those potentially applicable forms of estoppel operate to preclude assertion of rights by parties to proceedings. But they do so in ways not adequately differentiated in the reasoning of the Full Court. In the context of the property settlement proceedings and the spousal maintenance proceedings, claim estoppel would operate to preclude assertion by the wife of any right non-existence of which was asserted by the husband in the Dubai proceedings and finally determined by the ruling of the Dubai Court. Anshun estoppel would preclude assertion by the wife of any right which she could have asserted in the Dubai proceedings but which she chose to refrain from asserting in circumstances which made that choice unreasonable in the context of the Dubai proceedings.
…
34Founded on the twin policies of ensuring finality in litigation (thereby promoting respect for and efficient use of courts as well as avoiding inconsistent judgments) and of ensuring fairness to litigants (by sparing them the stress and expense of duplicative proceedings), the focus of the common law doctrine of estoppel is on 'substance rather than form'. The doctrine looks not for absolute identity between the sources and incidents of rights asserted or capable of being asserted in consecutive proceedings. The doctrine looks rather for substantial correspondence between those rights. Enough for its operation is that the rights are of a substantially equivalent nature and cover substantially the same subject matter.
(references omitted)

In Port of Melbourne Authority v Anshun Pty Ltd (1981) 147 CLR 589 (Anshun), Gibbs CJ, Mason J and Aickin J stated at (602) ‑ (603) that:
Generally speaking, it would be unreasonable not to plead a defence if, having regard to the nature of the plaintiff's claim, and its subject matter it would be expected that the defendant would raise the defence and thereby enable the relevant issues to be determined in the one proceeding.
Nearly thirty years later in DP World Australia Ltd v Fremantle Port Authority [2009] WASCA 16 (DP World), Newnes AJA [73], McLure JA agreeing, citing Henderson v Henderson (1843) 3 Hare 100; [1843-60] All ER Rep 378; (1843) 67 ER 313 and Anshun explained the Anshun principle in the following terms:
73The rule invoked by the appellant rests upon the principle that the court requires parties to litigation to bring forward their whole case and will not permit a party to reserve a claim and make it later when it could and should have been made in the earlier proceedings.
And later at [86] and [87], Newnes AJA stated the following:
86 It is clear, however, that Anshun estoppel does not operate simply because a party is asserting a cause of action which could have been, but was not, raised in a previous proceeding in which that party was asserting a different cause of action based on substantially the same facts against the same party. The touchstone is reasonableness; the question is whether it was unreasonable for the party asserting the cause of action in the second proceeding to have refrained from raising it in the earlier proceeding.
87 Whether it was unreasonable not to bring the claim in the earlier proceedings depends upon an examination of all the relevant circumstances, focussing on the issue of reasonableness. There can be no hard and fast rules. As the High Court pointed out (602) in Anshun, a party may legitimately refrain from litigating an issue in earlier proceedings for a variety of reasons such as expense, the importance of the particular issue, and motives extraneous to the actual litigation.
(references omitted)
I observe here that whether Anshun estoppel applies involves considering all of the relevant circumstances against the background touchstone of reasonableness.

H. The statutory scheme - the Workers' Compensation Act

The Act has recently been considered by a number of cases in the Western Australian Court of Appeal. In Beasley v Pilbara Mining Alliance Pty Ltd [2022] WASCA 25 (Quinlan CJ, Murphy JA & Tottle J) the court referred to the Act and made a number of relevant observations about its operation:
8The Act establishes a compulsory no fault workers' compensation insurance scheme covering the liability of employers for injuries suffered by employees in the course of their employment.
…
9Part III of the Act is headed 'Compensation'. It establishes the regime for compensating workers who suffer an 'injury'. 'Injury' has an expanded meaning and, relevantly, means 'a personal injury by accident arising out of or in the course of the employment, or whilst the worker is acting under the employer's instructions'.
10Section 18 expresses the central concept on which the regime established by pt III of the Act is based and provides, in effect, if an 'injury' of a worker 'occurs', then 'the employer shall, subject to this Act, be liable to pay compensation in accordance with Schedule 1'. Section 21 provides, relevantly, that an employer is liable to pay compensation under the Act from the date of incapacity resulting from injury. The effect of s 18 and s 21 has been held to impose a liability on an employer to pay compensation from the date of incapacity resulting from injury. Once incapacity is suffered, compensation is payable 'instanter'.
(references omitted)
The Rutherford Arbitration was principally concerned with s 58, s 61 and s 62 of the Act, which are found in pt III, div 5 of the Act. That division is titled 'Commencement, review, suspension, and cessation of payments'.
Section 58 and s 62 of the Act are in the following terms:
58.Liability for weekly payments, arbitrator may determine
(1)Where, in the circumstances mentioned in section 57A(1) -
(a)a period of 19 days has elapsed since those circumstances arose and the worker has not received the first of the weekly payments claimed; or
(b)whether or not the period mentioned in paragraph (a) has elapsed, notification has been given by the insurer -
(i)under section 57A(3)(b) or 57A(3a)(b), that liability is disputed; or
(ii)under section 57A(3)(c), that a decision as to liability is not able to be made within the time allowed, an arbitrator may, on the application of the worker hear and determine the question of liability to make the weekly payments claimed.
(2)Where in the circumstances mentioned in section 57B(1) -
(a)a period of 17 days has elapsed since those circumstances arose and the worker has not received the first of the weekly payments claimed; or
(b)whether or not the period mentioned in paragraph (a) has elapsed, notification has been given by the employer -
(i)under section 57B(2)(b) or 57B(2a)(b), that liability is disputed; or
(ii)under section 57B(2)(c), that a decision as to liability is not able to be made within the time allowed, an arbitrator may, on the application of the worker hear and determine the question of liability to make the weekly payments claimed.
(2a)Where under section 57A(3a) or 57B(2a) a claim by a worker is deemed to be disputed, the Director may order the employer to make an application for an arbitrator to hear and determine the question of liability to make the weekly payments claimed.
(3)An employer may, in the circumstances mentioned in section 57A(1) or section 57B(1), make application for an arbitrator to hear and determine the question of liability to make the weekly payments claimed, and an arbitrator may hear and determine the matter.
[(4) deleted]
(5)On a hearing under subsection (1), (2), (2a) or (3) the arbitrator is to satisfy himself as to all the evidence before him and -
(a)if the arbitrator considers that the evidence is satisfactory to establish liability to make weekly payments, may -
(i)make an order that weekly payments including arrears to the date of the hearing shall be paid out of moneys standing to the credit of the General Account and that the employer shall forthwith pay to WorkCover WA for the General Account the amount of such payments together with an additional 10% of that amount; or
(ii)make an order as to weekly payments by the employer to the worker on such terms as the arbitrator sees fit; or
(b)if the arbitrator considers that the evidence is not satisfactory to establish liability to make weekly payments, may dismiss or adjourn the application on such terms as the arbitrator sees fit.
(6)The fact that an application has been dismissed under subsection (5) shall not be taken into account by an arbitrator in any other proceedings under this Act.
…
62.Reviewing and discontinuing, suspending or changing weekly payments
(1)Any weekly payment may be reviewed by an arbitrator on an application either of the employer or of the worker, and on such review, may be discontinued, reduced, or increased subject to any maximum provided, as from such date as the arbitrator, having regard to the past or present condition of the worker, sees fit.
(2) An arbitrator may, instead of discontinuing, reducing or increasing the weekly payments, suspend the weekly payments from the date of the order until such time as is specified in the order.
Arbitrator Rutherford was aware of the very different enquiry that arises under s 58 from one brought under s 62. In the Rutherford Decision, Arbitrator Rutherford stated as follows:
131River Hill does not admit that that Mr Moore suffered an injury to the L4/L5 area nor any psychological injury. Further, and as far as I am aware, Mr Moore has made no specific further claim for either such additional injury/condition pursuant to the provisions of ss 18, 21, 57, 58 and 178 of the Act. Even if he has, such a claim is not before me i.e. there is no application for determination for liability brought within s 58 of the Act, assuming the provisions of ss 178 and 179 have been complied with.
132In my view, a hearing of an application to establish the liability of an employer for workers' compensation payable pursuant to s 18 and s 21 of the Act involves a very different enquiry to one brought within s 62 of the Act. Section 62 requires a review of any weekly payment having regard to the past and present condition of the worker. Although not specifically stated to be a review in relation to an established or admitted injury, that must be the case as the obligation to make weekly payments is predicated on the employer being liable to make payments for an admitted or prior determined injury after the hearing of an application brought within s 58 of the Act. Importantly, to be able to bring a s 58 application, the requirements of ss 57 A, 178 and 179 are to be met.
133In other words, for there to be an injury within the provisions of the Act, that injury needs to be the subject of a claim for that injury and which claim is either admitted or the subject of a successful application. The worker needs therefore to have complied with s 178 and s 179 i.e. the notification of an occurrence and the subsequent making of a claim for that alleged injury accompanied by a First Certificate of Capacity.
As Arbitrator Rutherford observed, one of the fundamental differences between s 58 and s 62 is that s 62 necessarily involves an established or admitted injury. Though not expressly contained in s 62, that is implicit in its operation, as it deals with the review of existing weekly compensation payments.
Further, an element of the statutory scheme is that once weekly payments have been commenced, an employer is not permitted to reduce or discontinue them other than as authorised by the Act: Regis Aged Care Pty Ltd v Hunter [2018] WASCA 50 [48], citing with approval Department of Education v Kenworthy (1990) 3 WAR 1, 17; Taylor v Star Broken Meats (Unreported, WASCA, Library No 920434, 26 August 1992) 9 (Owen J).
As set out above, Arbitrator Rutherford conducted the arbitration on the basis that River Hill did not admit Mr Moore's L4/L5 injuries and there was no claim made in respect of those injuries pursuant to the provisions of s 18, s 21, s 57, s 58 or s 178 of the Act: Rutherford Decision [131].
In his written submissions, Mr Moore's counsel made a number of submissions about the Act:
(a) first, the legislation is remedial legislation and as such should be construed for the benefit of workers;
(b) secondly, in the context of the dispute resolution provisions under pt XI of the Act, the objects of that part are to provide a fair and cost effective system for the resolution of disputes that is timely, accessible, minimises costs to the parties, and in the case of arbitrations, enables disputes not resolved by conciliation, to be determined according to their merits with as little formality and technicality as practicable (s 177);
(c)thirdly, an arbitrator is to act according to equity, good conscience and the substantial merits of the case without regard to technicalities and legal forms (s 188(2)(b)); and
(d)one of the purposes of the Act is to make provision for the hearing and determination (by the dispute resolution authorities) of disputes between parties involved in workers' compensation matters in a manner that is fair, just, economical, informal and quick (s 3(d)).
In his oral submissions, Mr Moore's counsel said that the statutory scheme was set up for the benefit of workers and gave various examples of how that was manifested in the Act. By way of example, counsel submitted that a party could make multiples claims under s 58 of the Act, which arose out of the same injury (ts 59, ts 60). A similar argument applied to s 62 of the Act.

Ground 1: was Mr Moore estopped by cause of action estoppel?

I.1 River Hill's submissions - cause of action estoppel

River Hill's central submission was to the effect that s 58 and s 62 of the Act involved the same causes of action in that there was substantial correspondence between the rights asserted in both proceedings and the rights were of a substantially equivalent nature and covered substantially the same subject matter. This was submitted in several different ways.
River Hill's written and oral submissions in support of the appeal can be summarised as follows.
First, River Hill submitted that Arbitrator Nunn committed a mixed error of fact and law in finding at [54] of his decision that Mr Moore was not estopped by cause of action estoppel. That submission rested on the distinction that Arbitrator Nunn drew between proceedings under s 58 and s 62 of the Act. It also rested on Arbitrator Nunn finding that Mr Moore had not made a claim in relation to his L4/L5 injury: River Hill Submissions (RHS), par 5.
River Hill submitted that reliance on those matters was wrong as a matter of principle, in relation to both cause of action estoppel and Anshun estoppel: RHS, par 6. River Hill submitted at par 7 that:
The principles in relation to cause of action estoppel require 'substantial equivalence' between the subject matter of two causes of action and caution against elevating substance over form. (emphasis added)
I observe here that River Hill's summary of principle is not supported by Clayton, in particular, at [34], which is set out above. Kiefel CJ, Bell and Gageler JJ stated that the focus of the common law doctrine of estoppel is on substance rather than form. Their Honours then explained how that occurred:
The doctrine looks not for absolute identity between the sources and incidents of rights asserted or capable of being asserted in consecutive proceedings. The doctrine looks rather for substantial correspondence between those rights.
Secondly, River Hill submitted that Arbitrator Nunn was required to compare the causes of action in A56736 and A96333. River Hill submitted that the remedy, the injuries and the workplace accident were all the same: RHS, par 23.
Thirdly, River Hill submitted that Arbitrator Nunn wrongly drew a distinction between a s 62 dispute and a s 58 dispute: RHS, par 25. Those sections were merely 'gateways through which parties wishing to obtain resolution of particular disputes may then pass' (Kuligowski v Metrobus (2004) 220 CLR 363, 377 [33]): RHS, par 26.
Fourthly, River Hill submitted that just because Mr Moore had not nominated s 58 did not diminish the 'substantial correspondence' between the rights asserted. For cause of action estoppel to apply, it was not necessary that the source of the asserted rights was identical. It was sufficient if they were substantially equivalent and covered substantially the same subject matter: Clayton (49) [34] (Kiefel CJ, Bell & Gageler JJ); Tomlinson, [22]: RHS, par 27.
Fifthly, in its written submissions, River Hill submitted that the focus of the doctrine was on substance rather than form: RHS, par 29. In the next paragraph of River Hill's written submissions, being par 30, River Hill submitted as follows:
The fact that the respondent did not rely upon s 58 of the WCIMA as an alternative to s 62 of the WCIMA in A56736 should not have been found by the arbitrator to preclude the operation of cause of action estoppel in A96333. That finding elevated substance over form, in preference to the substantial equivalence between the two causes of action.
(emphasis added)
In correspondence after the hearing, solicitors for River Hill sought to correct the above par 30 of its written submissions such that the paragraph read 'that finding elevated form over substance'.
Having regard to the oral submissions of River Hill's counsel and River Hill's correspondence, I understand River Hill to be submitting, in effect, that Arbitrator Nunn did not give sufficient consideration to the substance of Mr Moore's claim in respect of his L2/L3 and L4/L5 injuries. Arbitrator Nunn's attention and focus was (wrongly) on the form in which Mr Moore made his claim in the Rutherford Arbitration (i.e. a claim under s 62) and not the substance of what Mr Moore claimed.
Sixthly, River Hill submitted that Arbitrator Nunn found at [38] that the causes of action were not the same, that is, that s 58 and s 62 of the Act were not the same. Arbitrator Nunn should have found that the causes of action were the same, in that there was substantial correspondence between the rights asserted in both proceedings and the rights were of a substantially equivalent nature and covered substantially the same subject matter: RHS, pars 31 - 38.
At the hearing of the matter, River Hill's counsel developed these submissions.
He said that the key issue in relation to cause of action estoppel was whether there was substantial equivalence between the subject matter of the two causes of action (ts 2, ts 8). Counsel said that Mr Moore had put in issue all parts of his lower back during the Rutherford Arbitration (ts 9).
Counsel submitted that Arbitrator Nunn had made a finding at [5] of his decision, which dealt with all parts of Mr Moore's lower back, and that it was not possible to challenge that finding (as it had not been appealed) (ts 23, ts 24).
Paragraph 5 of Arbitrator Nunn's reasons is in the following terms:
5.In the alternative, he sought a review of those weekly payments under s 62 claiming that he remained incapacitated as a result of both his L2/L3 injuries and an L4/L5 condition aggravated in the original injury and a psychological condition.
River Hill's counsel submitted that Mr Moore claimed rights that were substantially equivalent in nature and covered the same subject matter. In this regard, Mr Moore had sought a remedy in the Rutherford Arbitration, which involved weekly payments of compensation for all parts of his back (which I understand to mean both his L2/L3 injuries and his L4/L5 injuries) and for his psychological injury (ts 10, ts 11).
Counsel submitted that [5] of Arbitrator Nunn's reasons was a finding demonstrating that Mr Moore had already made a claim about his alleged injury to L4/L5, which had been adjudicated (ts 11). Put differently, River Hill's counsel submitted that Arbitrator Rutherford had decided Mr Moore's s 62 claim and that had included all parts of Mr Moore's back (ts 16, ts 17, ts 21).
Further, counsel submitted that it was not necessary to review Arbitrator Rutherford's reasons for reaching the conclusion that he reached (ts 17). What mattered was his conclusion only, not his reasons for that conclusion. Support for this was said to be found in a decision of the Federal Court concerning Zetta Jet Pte Ltd v The Ship 'Dragon Pearl' (No 2) [2018] FCAFC 132 (Zetta) [47] - [51] (Allsop CJ, Moshinksky & Colvin JJ).
Zetta was a case involving res judicata. In that case, the court held that there was no need to inquire into the particular circumstances in which a final judgment was obtained in order to determine whether a res judicata arose. The principle was not dependent on a determination of the merits. The relevant question involved an inquiry into whether the cause of action had been adjudicated by the final judgment. That involved in essence, a review of the record (being the nature of the claim and final orders sought).
River Hill's counsel submitted that the Rutherford Arbitration involved medical evidence concerning Mr Moore's L4/L5 claim, albeit not comprehensive, and a decision by Arbitrator Rutherford that went to the merits of the claim as made. It was not necessary to consider Arbitrator Rutherford's reasons (ts 15, ts 16). In effect, Arbitrator Rutherford dismissed Mr Moore's application under s 62 and that was all that was necessary (ts 17, ts 21).

I.2 Mr Moore's submissions - cause of action estoppel

Mr Moore's written and oral submissions in opposition to the appeal can be summarised as follows.
First, the Act does not provide for a single cause of action but rather creates a number of rights a worker is entitled to pursue independent of other rights. In other jurisdictions, similar legislation has been held to entitle a party to be compensated separately in respect of disparate injuries sustained in the same accident: in effect, a party may pursue separate claims for injuries arising out of the same event: see for example Salmon Street Ltd (In Liquidation) formerly General Motors‑Holden's Limited v Jorgensen (1992) 56 SASR 158, 161 (Salmon Street): Moore Submissions (MS), par 20.
The statutory scheme was consistent with separate claims being made for separate injuries arising out of the same accident. In the present case, Mr Moore was not required to bring a single application containing every claim that he had or may have had against River Hill in respect of every injury he sustained on 5 May 2017. In his oral submissions, Mr Moore's counsel repeated that the statutory scheme was established for the benefit of workers, entitling workers to make multiple claims arising out of the same incident (ts 65).
Secondly, Arbitrator Nunn identified the relevant cause of action principles as outlined in cases such as Clayton and Trawl Industries of Australia Pty Limited (in liquidation) v Effem Foots Pty Ltd (1992) 36 FCR 406. Arbitrator Nunn correctly identified that Mr Moore's L4/L5 injury was not 'litigated' in A56736: in A56736, Arbitrator Rutherford considered only the 'accepted injuries' (being the L2/L3 injury) when considering the claim under s 62 of the Act. That did not include Mr Moore's L4/L5 injury: MS, pars 20 - 21.
Thirdly, Mr Moore submitted that River Hill had, in its appeal notice at ground 1(c), stated that Mr Moore's two applications dealt with the '… the same body part, being the lower back …' In contradistinction to this, the very argument that River Hill ventilated in A56736 was that Arbitrator Rutherford had no power to consider injuries other than the accepted injuries (being the L2/L3 injuries). In effect, River Hill seemed to be arguing both sides. In any event, the statutory regime did not require Mr Moore to bring every claim he may have against River Hill in the same arbitration: MS, pars 23 - 25.
In his oral submissions, Mr Moore's counsel submitted that River Hill's submission was wrong, because the claims did not involve the 'same body part' (i.e. L2/L3 injury versus L4/L5 injury). The L4/L5 injury had not been substantively determined (ts 69).

I.3 Disposition

I largely agree with Arbitrator Nunn's reasons for dismissing the application. I set out below in summary form my brief reasons for reaching this conclusion.
First, the legislative scheme created by the Act permits separate claims for different injuries arising out of the same event. Neither party suggested otherwise. In the circumstances, Mr Moore was not compelled under the Act to bring every claim that he had or may have had against River Hill in respect of every injury he sustained on 5 May 2017 in one application. There is nothing in the statutory scheme which expressly required that action.
This construction of the Act finds support in similar legislation and case law that has considered it. By way of example, in Salmon Street, the court was asked to bar a claim on the basis of res judicata by virtue of a previous determination. In that case, the respondent had previously claimed compensation under the Workers Compensation Act 1971 (SA) for the loss of the sense of smell and taste, consequent upon a head injury. The respondent had later claimed compensation arising from the same head injury which resulted in vertigo. King CJ (with whom Cox & Bollen JJ agreed) stated at page 162 that:
In my opinion a worker who seeks to have a disputed right to compensation in respect of a particular injury determined by the Industrial Court is not required to raise in the proceedings all injuries or impairments which he has sustained in the accident or even all injuries or impairments of which he is then aware. He may obtain an award in respect of one or more injuries or impairments, and subsequently pursue his claim in respect of other injuries or impairments suffered in the same accident. If, however, a claim in respect of a particular injury or impairment is pleaded in the proceedings and is the subject of a determination either granting compensation or dismissing the claim, the claim in respect of that injury or impairment merges in the determination and subsequent proceedings for the determination of a disputed claim in respect of the same injury or impairment would be barred as res judicata. It is therefore necessary to examine the pleadings in the prior proceedings and the terms of the award in order to determine whether the subsequent claim is barred.
The claim in the present proceedings is for vertigo resulting from the head injury. The question is whether the claim in respect of that injury or impairment was determined by the consent order made in the prior proceedings.
In Salmon Street, the court held that the second claim was not an abuse of process, hence res judicata did not apply, as the worker had not been obliged to include the claim for vertigo in his earlier compensation claim for loss of the sense of smell and taste.
Although Cox J agreed with King CJ and Bollen J, he made some brief comments at page 164, which relevantly included the following:
[w]hile the Workers' Compensation legislation permits a worker to make successive claims for different injuries suffered on the one occasion, it is obviously desirable that all table injury claims, for instance, be made at the same time if that can reasonably be done, and it would be unfortunate if the decision in this case were to lead anyone to think otherwise.
Two things may be said about Cox J's statement of principle above. First, Cox J's express reference to 'desirable' recognises that the South Australian Workers Compensation Act 1971 did not bar or prevent or disqualify a party who later made a claim for a different injury arising from the same accident. In effect, the Workers Compensation Act 1971 did not mandate that all claims had to be made at the same time. In my view, similar considerations apply generally to the Act. Secondly, and in any event, Cox J's statement was obiter dicta. It was not something with which King CJ nor Bollen J expressly agreed.
The second reason for rejecting this ground focusses on what was litigated before Arbitrator Rutherford. In my view, Arbitrator Nunn correctly identified that Mr Moore's L4/L5 injury was not litigated in A56736. This was because Arbitrator Rutherford found, and it was not disputed, that Mr Moore had not made a claim with respect to his L4/L5 injuries (ts 27, ts 29). That is, Mr Moore had not made a claim for his L4/L5 injuries under s 18, s 21, s 57, s 58 and s 178 of the Act. Arbitrator Rutherford could only consider Mr Moore's 'accepted injuries' (being his L2/L3 injuries) when considering his claim under s 62 of the Act. In substance, Mr Moore's L4/L5 injuries were not litigated on their merits (or indeed heard at all).
River Hill submitted that the remedy, the injuries and the workplace accident were all the same. In this regard, River Hill submitted that Mr Moore had sought a remedy in the Rutherford Arbitration, which involved weekly payments of compensation for all parts of his back (both his L2/L3 injuries and his L4/L5 injuries and for his psychological injury). As Arbitrator Nunn found, whether Mr Moore was entitled to such compensation involved consideration of whether he suffered a compensable injury said to give rise to his incapacity. That issue was not litigated in the Rutherford Arbitration because only those injuries for which liability had been accepted or admitted could be included in a claim under s 62 (which was River Hill's submission before Arbitrator Rutherford, on which it was successful). In summary and contrary to River Hill's submission, whether Mr Moore had a valid claim in respect of his L4/L5 injuries - including whether Mr Moore sustained an L4/L5 injury in the course of his employment - was not determined in the Rutherford Arbitration and has yet to be determined: cf Tomlinson [22].
Thirdly, Arbitrator Nunn stated that there were procedural and jurisdictional questions involving s 57A and s 178 of the Act which would ordinarily be addressed first, before considering Mr Moore's claim under s 62. Going straight to s 62 and by-passing these provisions was inconsistent with the ordinary operation of the Act. It would also be inconsistent with Arbitrator Rutherford's obligation to act according to the rules of natural justice (s 188(1)).
Fourthly, consideration and resolution of a claim under s 62 does not involve the same consideration as a claim under s 58 of the Act. Although there are some aspects that are similar, a claim asserted under s 62 and a claim asserted under s 58 are not 'substantially equivalent' as that term is understood. As Arbitrator Nunn observed at [47]:
[t]he right infringed is not the right to compensation, but rather the right to agitate for compensation if liability for an injury is not admitted. That is the process provided for by s 57A and s 58.
On the other hand, a claim involving s 62 assumes, implicitly, an admitted or agreed claim. That was not the case here. As may be recalled, in the Rutherford Arbitration, River Hill submitted that Arbitrator Rutherford had no power to consider injuries other than the accepted injuries (being the L2/L3 injuries). River Hill was successful in that submission before Arbitrator Rutherford. There are also different factual enquiries involved in resolving disputes under s 58 and s 62.
Fifthly, even if Arbitrator Rutherford wanted to arbitrate the two claims at the same time, he did not have the power to do so (as he found). Arbitrator Rutherford could not compel Mr Moore to make a claim for his L4/L5 injuries. Arbitrator Rutherford did not have power to consider a claim under s 62, absent an admitted or agreed claim. If Mr Moore had made a claim relating to his L4/L5 injuries earlier, and depending on when that occurred, Arbitrator Rutherford's power to hear such a claim would have rested on the parties agreeing to allow him to hear that claim concurrently with his L2/L3 injuries claim and/or have it consolidated into the same existing arbitration. How that would have affected the existing arbitration, including whether the claim would have needed to go through the conciliation provisions contained in the Act etc, would have had to be considered.
In this regard, it should be observed that the objects of a claim asserted under s 62 and a claim asserted under s 58 are very different. Arguably, claims involving reviewing and discontinuing, suspending or changing weekly payments under s 62 should be dealt with quicker, and less formally, having regard to the operation of the Act and the existing (i.e. admitted or determined) claim which underpins the rights being asserted. In contrast, an arbitrator's determination of liability under s 58 is likely to take longer, given the very different factual enquiry involved (as Arbitrator Nunn observed).
Sixthly, River Hill's submission that Mr Moore should have made a claim for his L4/L5 injuries has a further difficulty. The claim form Mr Moore signed asked him to identify his 'most serious injury'. On Mr Moore's case, that is what he did. It was also the basis on which River Hill's insurer admitted liability. Mr Moore was not asked to identify every injury he suffered, which appears to be River Hill's position. In my view, it would be a perverse outcome if Mr Moore was found to have claimed his L4/L5 injuries and had them adjudicated in circumstances where his claim form did not require all claims to be made simultaneously. There was no reference to his L4/L5 injuries and Arbitrator Rutherford did not adjudicate that claim.
Seventhly, having regard to the legislative framework, the purpose and objects of the Act, the matters below, and the fact that the Act permits multiple claims to be made arising out of the same accident, tends to suggest that estoppel, particularly cause of action estoppel and Anshun estoppel principles have a limited role to play under the Act:
(a)the statutory scheme prescribes that arbitrations are normally conducted in private: s 199;
(b)although reasons are often given to the parties, those reasons are not published: Nunn Arbitration, [15] - [21];
(c)ordinarily, one arbitrator under the Act cannot and does not bind another arbitrator. That was Arbitrator Nunn's position when he heard River Hill's submission: see [21], [33]; and
(d)the parties could not locate a Western Australian case that had applied cause of action estoppel to the Act.
Eighthly, River Hill submitted that it was not possible to challenge [5] of Arbitrator Nunn's reasons, because it was a finding that Mr Moore had made a claim in the Rutherford Arbitration concerning all parts of his lower back, which had been adjudicated. Three things may be said about that submission. First, the submission was an oral submission and did not form part of River Hill's grounds. Secondly, Arbitrator Rutherford found that Mr Moore had not made a claim with respect to his L4/L5 injuries, which was River Hill's submission at that time (e.g. ts 27, ts 29). Thirdly, although it might be said that Mr Moore had sought a remedy in respect of all parts of his lower back in the Rutherford Arbitration, Arbitrator Rutherford did not adjudicate Mr Moore's substantive rights in relation to his L4/L5 injuries as Mr Moore had not made a claim. Given the provisions of the Act and Arbitrator Rutherford's findings, Mr Moore was entitled to make a claim in respect of his L4/L5 injuries and have that claim adjudicated.
Ninthly, River Hill submitted that Arbitrator Nunn erred in fact in finding at [39(c)] and [39(d)] that its submissions were limited to the question of incapacity: particular (e) to ground 1. In my view, River Hill's submission mischaracterises Arbitrator Nunn's reasons. Having regard to Arbitrator Nunn's reasons generally, including how Arbitrator Nunn identified the issues ([11] - [13] and [42] - [44]), and summarised the estoppel arguments generally ([22] - [33]), and his reasons ([44] ‑ [54]), it is clear to me that Arbitrator Nunn understood and addressed the breadth of River Hill's claim, as he summarised at [35] and [36] and for the reasons he gave. Further, if an error was made, it was not an error of law: an error of fact alone is not sufficient: BHP Billiton [5]. And, if the error did involve an error of law, River Hill has not demonstrated that the error was material, in the sense that, but for the error, the decision would have been or might have been different: BHP Billiton [15]; Australian Broadcasting Tribunal (353).
Finally, Zetta has limited application in the present circumstances. In the present case, the matters in issue concern cause of action estoppel and Anshun estoppel, not res judicata, as was the case in Zetta. Further, Arbitrator Rutherford did not consider the merits of Mr Moore's L4/L5 injuries. A claim under s 62 assumes an entitlement on the basis that a claim has been made (and admitted or determined). Lastly, Zetta was not concerned with claims under the Act.
In summary, I find that River Hill's first ground of appeal discloses no error of law. Arbitrator Nunn's reasons for dismissing this part of River Hill's application do not reveal error.

J. Ground 2: was Mr Moore estopped by reason of Anshun estoppel?

J.1 Overview

By way of introduction, I observe that the common law principles of Anshun estoppel and cause of action estoppel overlap to a significant degree. For this reason, my reasons for rejecting River Hill's cause of action ground overlap with my reasons for rejecting River Hill's Anshun ground. It is not necessary for me to repeat each and every argument.

J.2 River Hill's submissions - Anshun estoppel

River Hill's principal submission was that because of the Anshun principle, Mr Moore was required, 'acting reasonably', to do 'whatever was necessary so as to bring forward his whole case rather than reserving it and making it later': RHS, par 45. That submission was developed in a number of ways and can be summarised as follows.
First, Arbitrator Nunn committed a mixed error of fact and law in finding at [73] of his decision that Mr Moore was not estopped by Anshun estoppel. Anshun estoppel requires parties to plead alternative claims rather than reserving alternative claims for subsequent proceedings.
Secondly, River Hill submitted that just because Mr Moore did not make a formal claim nominating s 58 of the Act in the Rutherford Arbitration, that did not preclude the operation of Anshun estoppel: RHS, pars 8 - 9. That submission was made in the context where in the Rutherford Arbitration, Mr Moore sought orders recommencing his weekly payments of compensation for total incapacity from 1 July 2018 under s 62 of the Act.
Thirdly, River Hill submitted that Arbitrator Nunn was wrong to find (at [67]) that, given Mr Moore had not made a claim for his L4/L5 injury, no legal argument could arise in relation to liability for his L4/L5 injury under s 58 of the Act at that time. In effect, that finding was contrary to the Anshun principle that required Mr Moore to raise alternative claims unless it would be unreasonable to do so: RHS, pars 39 - 52.
At the hearing of the appeal, River Hill's counsel submitted that the key issue in Anshun estoppel is the requirement to plead alternative claims, rather than reserving alternative claims and waiting for the outcome of the first application and then pursuing it later, if the outcome is not positive (ts 2).
River Hill's counsel submitted that even though Mr Moore became aware of his L4/L5 injuries after commencing his application for arbitration before Arbitrator Rutherford, Anshun principles required him to make a claim and bring that claim before Arbitrator Rutherford as soon as possible, and preferably before Arbitration Rutherford heard and determined the application before him (ts 30 - ts 34, ts 51). In the arbitration before Arbitrator Rutherford, Mr Moore had medical evidence to the effect that he had an injury to his L4/L5: in those circumstances, River Hill's counsel submitted that Mr Moore should have made a claim for those injuries at that time and the failure to do so was unreasonable (ts 35, ts 38).
In exchanges with the bench, it became apparent that River Hill had assumed that if Mr Moore had made a new/additional claim as suggested, that it would have been heard by the same arbitrator - being Arbitrator Rutherford. i.e. in a consolidated arbitration. As that discussion developed, River Hill's counsel accepted that this would have required an application to amend the existing application so that Arbitrator Rutherford could hear both applications together (ts 42, ts 43).
River Hill's counsel did not identify the power under the Act that would enable Arbitrator Rutherford to hear Mr Moore's second claim, if he had been minded to make a separate claim at that time. And when it was suggested to River Hill's counsel that River Hill might have objected to such consolidation/amendment, counsel responded, saying 'but that's all speculation, that that doesn't assist the respondent' (ts 46, ts 47).
Finally, in exchanges with the bench, River Hill's counsel accepted that it was open to an applicant to make multiple claims for different injuries over a period of time assuming they arose out of the same event. River Hill's counsel submitted that the difference in the present circumstances was that Mr Moore brought 'the application' seeking the same remedy for the 'very same injuries' (ts 54). The 'application' was a reference to A56736 - being the application before Arbitrator Rutherford (ts 54, ts 55).

J.3 Mr Moore's submissions - Anshun estoppel

Mr Moore's submissions in opposition to the appeal can be summarised as follows.
First, Mr Moore submitted that the principles of Anshun estoppel should only be applied in the clearest of cases, given that they terminate a party's rights to have a court adjudicate the merits of its claim: MS, pars 26 - 28.
Secondly, Mr Moore submitted that there was significant overlap between Anshun estoppel and abuse of process. In the present case, Mr Moore did not make a conscious choice to refrain from claiming his L4/L5 injury in the Rutherford Arbitration. In any event, Mr Moore did not act unreasonably by not making a claim for his L4/L5 injury: MS, pars 29 - 32. In his oral submissions, Mr Moore's counsel said that Mr Moore's conduct could not be said to involve 'bad behaviour' such that it involved an abuse of process (ts 63).
Thirdly, Mr Moore submitted that the most recent High Court consideration of Anshun principles was in UBS AG v Tyne [2018] HCA 45. In that case, Gageler J stated at [69] that whether a claim sought to be brought in later proceedings was relevant to the subject matter of the earlier proceedings so that it would have been unreasonable not to have been brought, involves a normative judgment: MS, pars 32 - 39. Mr Moore submitted that where a normative judgment was concerned, it was incumbent on River Hill to identify the decision maker's (Arbitrator Nunn's) error, consistent with the principles in House v The King (1936) 55 CLR 499. Having regard to the House v The King principles, River Hill had not identified Arbitrator Nunn's error (although not expressly stated in the written submissions, it may be inferred that that was the effect of the written submission). In contradistinction to this, Arbitrator Nunn identified the correct principles. In the circumstances of the case, including the statutory scheme which permits multiple claims, it was reasonable of Mr Moore to not bring a s 58 claim in respect of his L4/L5 injuries at the same time as his s 62 application for continuation of payments in relation to his L2/L3 injuries.
In his oral submissions, Mr Moore's counsel submitted that at the time of the s 62 application, it was not unreasonable for Mr Moore to rely on his L2/L3 injuries, because at that time, the medical evidence suggested that he was 'still suffering from the L2/L3 protrusion at that point'. Mr Moore's written submissions at par 37 referred to the relevant medical evidence before Arbitrator Rutherford (ts 60). What was sought at the time, was the review of weekly payments for an accepted injury (ts 62).
Fourthly, Mr Moore's counsel submitted in his oral submissions, that under the scheme of the Act, disputes will first be subject to conciliation, and if conciliation is not able to resolve the dispute, then a party may apply to have the dispute made subject to arbitration before an arbitrator (ts 58). I understood this submission to refer to pt XI of the Act, particularly s 182ZT. In effect, if Mr Moore had made a claim under s 58 of the Act, then he would have to go through the conciliation regime in the Act before he could arbitrate his claim.
Fifthly, Mr Moore's counsel also submitted that if Mr Moore had made a separate claim in respect of his L4/L5 injuries, Arbitrator Rutherford could have adjourned the existing matter before him, although this assumed that Mr Moore could have satisfied Arbitrator Rutherford of the exceptional circumstances for that adjournment. And any adjournment would likely have involved the adjournment of the hearing for six months, if granted. Mr Moore's counsel was not aware of a similar situation as the one submitted by River Hill's counsel (ts 59).
Mr Moore's counsel submitted that given the statutory scheme, which enables multiple claims by workers and was set up for the benefit of workers, there was no basis for Anshun estoppel to apply (ts 60).

J.4 Disposition

I find that River Hill's second ground of appeal discloses no error of law. Arbitrator Nunn's reasons for dismissing this part of River Hill's application do not reveal error. I set out below my brief reasons for reaching this conclusion.
First, the dispute before Arbitrator Nunn concerned s 58(1) of the Act. That section, as Arbitrator Nunn found, is predicated on the circumstances mentioned in s 57A existing. Section 57A(1)(a) applies where there has been a claim for compensation against an employer under s 178(1)(b). Arbitrator Nunn found that that was the determinative factor in considering whether Anshun estoppel applied.
In the Rutherford Arbitration, the circumstances in s 57A did not exist because Mr Moore had not made a claim in respect of his L4/L5 injuries. Arbitrator Nunn found, in effect, that it was not possible for Mr Moore to bring a dispute in the Rutherford Arbitration under s 58 as Mr Moore had not made a claim to that effect. Similar reasoning was determinative of any application Mr Moore had as to s 62 in the same arbitration. And in the absence of a claim, there could be no legal argument as to River Hill's liability for Mr Moore's L4/L5 injuries. In the circumstances, Arbitrator Nunn found, in effect, that Mr Moore had not reserved a claim (under s 58) so that he could make it later (in the Nunn Arbitration): cf DP World [73].
Secondly, as Mr Moore's counsel submitted, it was not unreasonable for Mr Moore to rely on his L2/L3 injuries at the time of his application as that was consistent with Mr Moore's medical evidence. It was also consistent with River Hill's insurer's admission of liability. It was also consistent with the compensation form that Mr Moore had completed. And as matters ultimately evolved, Mr Moore did try to press his L4/L5 injuries in the Rutherford Arbitration, but was prevented from doing so because he had not complied with the Act's formalities.
Thirdly, for similar reasons, I do not think it can be said that Mr Moore's conduct involved 'bad behaviour' such that it involved an abuse of process.
Fourthly, it is well recognised that shutting a party out of an action is a serious step which should not be taken lightly for risk of serious injustice: DP World [83]. In my view, if there is any doubt about the outcome of this matter, then Mr Moore should receive the benefit of that doubt. This is not a clear case which warrants terminating Mr Moore's rights to adjudicate his claim. If Mr Moore were to secure compensation in A96333, that outcome would not be inconsistent with the decision in A56736 (Arbitrator Nunn made a similar observation at [57(b)] and [70] - [72], though in more restrained terms).
Fifthly, as to River Hill's submission that Mr Moore should have brought his claim for his L4/L5 injuries in the Rutherford Arbitration, that submission rested on the common law principles of Anshun estoppel, as I understood it. Put differently, it was not mandated by the Act, save for the requirements of s 178(b), which require proceedings for compensation with respect to an injury to commence within 12 months of the injury.
River Hill's submission appears to raise the following considerations and/or complications:
(a)because Mr Moore became aware of his L4/L5 injuries after commencing his application for arbitration before Arbitrator Rutherford, any subsequent claim he made would involve a new application under the Act;
(b)ordinarily a new application would be subject to the conciliation regime contained in the Act before it could be arbitrated. It is only if the dispute is not resolved by conciliation that a party may seek to resolve the dispute by arbitration;
(c)River Hill submitted that Arbitrator Rutherford could hear that new application (which seems to be dependent on the parties and the arbitrator agreeing to that course), but Mr Moore could not force Arbitrator Rutherford to hear that new application otherwise;
(d)for Arbitrator Rutherford to hear the new application at the same time as the existing A56736 arbitration, would involve consolidating the two arbitrations (assuming that an agreement could be reached with Arbitrator Rutherford and River Hill) so that Arbitrator Rutherford could hear them together; and
(e)at face value, it seems that there would be delay, and perhaps significant delay, if the two arbitrations were consolidated and heard together by Arbitrator Rutherford. This is in circumstances where Mr Moore was, by his first application, seeking review of weekly payments for an accepted injury and not seeking to have liability determined in respect of an injury.
It also must be remembered that Arbitrator Rutherford was expressly bound by rules of natural justice (s 188(1)).
Having regard to the purpose and objects of the statutory regime, including fairness, justice and speed, the operation of the Act with respect to claims and the circumstances of this case, it was not unreasonable for Mr Moore to rely on his L2/L3 injuries at the time of his application before Arbitrator Rutherford. Further, possession of medical evidence of a different injury arising out of the same incident does not, in and of itself, compel the conclusion that Mr Moore should have made a claim for that injury. The Act does not mandate claims in those circumstances. And in any event, consistent with DP World, the touchstone is reasonableness. Mr Moore did not act unreasonably in the circumstances.
Sixthly, as to Mr Moore's House v King submission, it seems to me that River Hill's complaint is that Arbitrator Nunn should have found that the subject matter of Mr Moore's L4/L5 injuries was so closely connected with A56736, that Mr Moore should have properly raised that claim in A56736. For reasons already advanced, the governing criterion is reasonableness.

K. Conclusion

For the above reasons, I grant River Hill leave to appeal but order that the appeal be dismissed.
I will hear from the parties as to the orders that should be made and as to costs.

I certify that the preceding paragraph(s) comprise the reasons for decision of the District Court of Western Australia.
SZ
Associate to Commissioner Collins
28 JUNE 2022