The State of Western Australia v Chown
[2025] WASC 116
•10 APRIL 2025
JURISDICTION : SUPREME COURT OF WESTERN AUSTRALIA
IN CRIMINAL
CITATION: THE STATE OF WESTERN AUSTRALIA -v- CHOWN [2025] WASC 116
CORAM: MCGRATH J
HEARD: 9 APRIL 2025
DELIVERED : 10 APRIL 2025
FILE NO/S: INS 11 of 2024
BETWEEN: THE STATE OF WESTERN AUSTRALIA
Prosecution
AND
REAGAN AINSLEY CHOWN
Accused
Catchwords:
Criminal law - Objection - Admissibility of expert evidence - Whether proposed witness an expert - Discretion to exclude - Probative value and prejudicial effect
Legislation:
Criminal Code (WA) s 279, s 280
Result:
Proposed testimony of expert witness admissible
Category: B
Representation:
Counsel:
| Prosecution | : | Mr J C Whalley SC |
| Accused | : | Mr P N Bevilacqua & Mr R Kashyap |
Solicitors:
| Prosecution | : | Director of Public Prosecutions (WA) |
| Accused | : | Peter Ash & Associates |
Case(s) referred to in decision(s):
Le‑Ta v The State of Western Australia [2020] WASCA 14
Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305
MCGRATH J:
The accused has been indicted on one count of murder contrary to s 279 of the Criminal Code (WA). The accused has pleaded not guilty and is proceeding to trial before a jury commencing on 30 April 2025.
The defence objects to the admissibility of a State proposed expert witness, namely Dr Ho, who will adduce testimony regarding the use of 'conducted electrical weapons' commonly referred to as 'tasers' and the effects of the discharge of a taser on a human. Dr Ho has prepared a written report which forms part of the State's prosecution brief of evidence. Further, counsel for the State posed a series of questions to Dr Ho arising from his written report, to which Dr Ho responded. The response of Dr Ho forms part of the proposed testimony. I have considered the written report and the correspondence.
The objection is based on a myriad of grounds. For the following reasons, I have determined that the proposed testimony of Dr Ho is admissible.
The State case at trial
To understand the contended relevance and admissibility of Dr Ho's evidence it is necessary that the alleged offending be outlined and the State case be particularised.
The State has filed an amended statement of material facts in the following terms:
(1)The deceased in relation to the murder charge was a 28‑year‑old male called Anthony John WOODS who was a serving officer with the West Australian Police Service.
(2)On Tuesday March 7th, 2023 the complainant in respect of the Steal Motor Vehicle charge parked and secured her motor vehicle, a white Holden Cruze registration 1EJB062, in a car park at 891 Canning Highway, Applecross.
(3)At about 4.55am that day, unknown offenders attended that location and stole the motor vehicle.
(4)At some point between Monday the 7th of March 2023 and Wednesday the 7th of June 2023, the accused came into possession of the stolen Holden Cruze and stored it at the rear of his house at [address redacted].
(5)On 7th June 2023 the accused was at his house at [address redacted] in company with a female associate with whom he smoked methylamphetamine during the day.
(6)At about 11pm the accused rang a male friend and asked him if he had any cannabis. On being informed that he did, the accused told the friend that he would come and pick him up.
(7)The accused then drove in the stolen Holden Cruze with his female associate to High Wycombe to collect his male friend. At this point the vehicle was bearing false number plates 1DLW565. (Count 1)
(8)At about 12.50am on 8 June 2023, the accused picked up the male friend who got into the rear of the car. With the accused driving and his female acquaintance in the front passenger seat, they started driving to the accused's house in [address redacted].
(9)At 1.01am the accused was driving in an easterly direction on Great Eastern Highway, Ascot.
(10)As the accused drove over the Great Eastern Highway and Tonkin Highway overpass, police were notified of the stolen vehicle via the Automatic Number Plate Recognition system and began to follow it as they conducted further checks on it.
(11)The accused manoeuvred his vehicle to the traffic-controlled intersection of Great Eastern Highway and Epsom Avenue Ascot.
(12)The accused brought his vehicle to a stop at the red traffic signal. As the traffic signal turned to green, the accused completed a right-hand turn and proceeded on Epsom Avenue.
(13)Police, having confirmed the motor vehicle was reported as stolen, approached the rear of the accused's vehicle and activated both emergency lights and sirens, signalling the accused to stop.
(14)The accused failed to stop and accelerated away from the police vehicle.
(15)As he did so, his male passenger was shouting at the accused to stop but the accused ignored him.
(16)The accused continued to accelerate his vehicle on Epsom Avenue and turned left into Ascot Place, Ascot.
(17)The environment the accused was travelling in is a built‑up residential area containing licensed premises and adjacent recreation areas.
(18)Pursuing police remained close to the accused's vehicle which was travelling at a speed of 100km/h in a 50km/h zone. The accused continued driving his vehicle in an attempt to evade police, and turned left into a cul-de-sac at a speed of between 70 and 80 km/h. (Count 2)
(19)As the accused approached the end of the cul-de-sac he slowed his vehicle and brought it to a stop.
(20)As he did so, the pursuing police vehicle stopped closely adjacent to it to attempt the apprehension of the accused.
(21)Constable WOODS exited the front passenger side of the police vehicle and approached the driver's door of the accused vehicle. Constable WOODS opened the driver's door which was immediately pulled closed by the accused.
(22)Constable WOODS again opened the front passenger door and clearly yelled instructions to the accused, 'Stay where you are'.
(23)The accused remained seated in the driver's seat of the vehicle, engaged reverse gear and began reversing the vehicle in an attempt to avoid being apprehended. As he did so Constable WOODS was standing between the open driver's door of the vehicle and the body of the vehicle.
(24)As the vehicle reversed, Constable WOODS became trapped in the wedge between the car body and the open driver's door. The rearward motion and positioning of the door meant that Constable WOODS was unable to escape the path of the vehicle and began being dragged.
(25)Constable WOODS again clearly yelled an instruction to the accused, 'Stay where you are'.
(26)The accused ignored Constable WOODS' instructions, instead continued driving the vehicle in reverse, with increasing speed, whilst Constable WOODS remained trapped in the wedge of the door.
(27)Constable WOODS deployed his police issued taser in an attempt to apprehend the accused.
(28)The accused continued accelerating heavily in reverse, crashing the vehicle through a set of wooden bollards and driving up onto the verge.
(29)Once on the verge he continued with heavy reverse acceleration, turned the vehicle sharply, and contacted a power pole stabilising wire then continued on, colliding into a second set of wooden bollards.
(30)All this occurred whilst Constable WOODS remained trapped between the open car door and the body of the vehicle. The vehicle's heavy acceleration and momentum made escape impossible.
(31)As a result of the accused's manner of driving, Constable WOODS fell from his standing position and became trapped underneath the vehicle. The accused continued his reverse acceleration and in doing so drove the vehicle over Constable WOODS, causing him to be trapped underneath the front right wheel.
(32)The combination of impact with the bollards and running over Constable WOODS brought the accused's vehicle to a stop.
(33)Constable WOODS' partner, Sergeant FISHER ordered the accused out of his vehicle at gun point. The accused attempted to get back into his vehicle at which point Sgt FISHER dragged him out, placed him on the ground and handcuffed him.
(34)Constable WOODS remained trapped underneath the vehicle in an unconscious state.
(35)Emergency response was coordinated including the use of numerous car jacks to raise the vehicle, which allowed first responding police to remove Constable WOODS from underneath the vehicle and to commence CPR prior to paramedics' attendance.
(36)Constable WOODS was conveyed to Royal Perth Hospital, Intensive Care Unit where he died on 11 June 2023 as a result of his injuries.
(37)At 1.25am on Thursday the 8th of June 2023, the accused was placed under arrest for numerous offences.
(38)He was conveyed to the Cannington Police Station where he subsequently participated in a record of interview shortly after 6pm on 8 June 2023.
(39)In that interview the accused admitted being the driver of the vehicle but claimed that his actions that resulted in the injury to Constable WOODS was a result of him being tasered. He stated that 'Without any warning I stopped, got shot with a taser and I couldn't move. I couldn't stop my body from doing what it was doing'.
(40)The accused also claimed that he had borrowed the Holden Cruze of a friend and that he did not know that it was stolen. He also claimed that he had not consumed any methylamphetamine since his release from jail some 3 weeks earlier.
(41)Following the death of Constable WOODS the accused was charged with murder and other offences.
(42)Toxicological analysis of a sample of blood taken from the accused following his arrest revealed zero alcohol and the presence of methylamphetamine at the level of 0.14 milligrams per litre.
(43)An examination of the stolen Holden Cruze by a trained police mechanic noted minor defects, but none that would have affected the accused's ability to control or operate the vehicle.
(44)A subsequent crash analysis established the when the accused's vehicle was passing the Swan Hotel on Epsom Avenue prior to turning into Ascot Place, it had been travelling at a conservative estimate of 83km/h in an area governed by a 50 km/h speed limit.
(45)A further analysis of the Taser deployment by Constable WOODS established that the accused's vehicle began to move backwards more than 2.5 seconds before Constable Woods deployed his Taser. (footnotes omitted)
The State's case in respect of the count of murder is based on the alleged intention of the accused to cause the deceased an injury of such a nature as to endanger or be likely to endanger his life contrary to s 279(1)(b) of the Criminal Code. That intention was allegedly formed when the accused put his vehicle into reverse motion when the deceased was trapped between the vehicle door and the body of the vehicle. It is alleged that the accused formed that intention when doing the act in order to avoid apprehension by the police.
In the alternative, the State relies upon manslaughter contrary to s 280 of the Criminal Code based upon criminal negligence (s 266 of the Criminal Code).
The State anticipates that the accused will rely upon a line of defence that he raised in his electronic record of interview with the police on 8 June 2023 (EROI). The accused contended that after being subjected to a discharge from the taser by the deceased, it was an involuntary bodily movement that was caused by his tasering which resulted in his vehicle reversing and, ultimately, the death of the deceased.
To establish the accused's guilt on the count of murder, the State will be required to prove beyond reasonable doubt that the act of putting the vehicle into reverse motion and causing the vehicle to move, was not an act that occurred independently of the exercise of the accused's will. In short, the State anticipates that the accused will rely upon s 23A of the Criminal Code.
The State further submits that in respect to the alternative count of manslaughter, whilst s 23A of the Criminal Code is expressly subject to the criminal negligence provisions of the Criminal Code, the question of whether the accused consciously and deliberately reversed his vehicle or if the movement of the vehicle resulted from an involuntary movement of the accused, arising from being subjected to tasering by the deceased, is likely to be highly relevant to the jury's assessment of whether the accused's conduct amounts to criminal negligence.
Relevant principles - expert evidence
The conditions for the admissibility of expert evidence were outlined by Heydon JA in Makita (Australia) Pty Ltd v Sprowles:[1]
(1)The subject matter of the opinion must fall within an established field of specialised knowledge; that is, the opinion evidence must go beyond the ordinary experience of the trier of fact.
(2)The witness must, by reason of training, study or experience, be an expert in that established field of specialised knowledge.
(3)So far as the opinion is based on facts 'observed' by the expert, they must be identified and admissibly proved by the expert; and so far as the opinion is based on 'assumed' or 'accepted' facts, they must be identified and proved in some other way.
(4)The process of inference that leads to the expert's opinion must be stated or revealed in a way that enables the conclusion to be tested and a judgment made about its reliability.
[1] Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305 [85].
The defence objections
The defence objects on a number of grounds to Dr Ho's evidence. The objections comprise:
(1)Whether the proposed evidence has a scientific basis. The defence submits that the proposed opinion does not fall within an established field of specialised knowledge. That is, the subject matter does not form part of a body of knowledge or experience which is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience, about which ordinary persons are not able to form a sound judgment without the assistance of the expert. Further, the evidence is unable to be tested.
(2)Whether Dr Ho is qualified to give the evidence.
(3)Whether Dr Ho is an independent expert given his employment with a private company.
(4)Whether Dr Ho's testimony considers an ultimate issue that the jury alone must determine.
Further, the defence submits that given the combined weight of the admissibility issues, I should find that the prejudicial value of Dr Ho's proposed testimony outweighs its probative value and that I should therefore exercise my discretion to exclude the proposed evidence.
Subject matter - established field of specialised knowledge/scientific basis
The defence submits that the opinion sought to be adduced is as to the 'musculoskeletal incapacitation effects from a taser … and what its human effects were in this case'.[2]
[2] Report of Dr Ho, page 1.
The defence submits there is no evidence that the physiological effects of tasers upon humans is an area of specialised knowledge as that term is commonly understood in expert evidence. That is, a field of knowledge that is widely acknowledged as involving formal recognition or accreditation. The defence submits that Dr Ho is not a neuro‑physician and that essentially Dr Ho is potentially an ad hoc expert.
In the defence submission, there is a complete absence of any robust alternative scientific endeavour or bodies to test Dr Ho's ideas and theory.[3]
[3] Defence Written Submissions [26].
The State submits that Dr Ho is a highly qualified medical practitioner who, by study and experience, is eminently qualified to give evidence concerning the effect of a taser discharge on the human body and the factors and variables involved in the effectiveness of any such discharge. Further, that Dr Ho has outlined his reasoning based upon his expert knowledge.
Dr Ho refers, in his report, to four reports concerning electrical weapon incapacitation and the effect of electrical weapon application on human volunteers. Further, Dr Ho has stated in the correspondence to counsel that his opinion is based upon his 23 years of taser testing comprising many different circumstances, probe positions and body compositions. In addition, as I outline below the extent of his academic writing has been extensive.
I am satisfied that Dr Ho provides an opinion that forms part of a body of knowledge or experience which is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience, about which ordinary persons are not able to form a sound judgment without the assistance of an expert. Further, I am satisfied that Dr Ho states his opinion in a manner that enables the conclusion to be tested and a judgment be made about its reliability.
I do not accept the defence submission that there is an insufficient empirical basis for the opinion. The contention is that there is no evidence concerning the actual measurement of the degree to which electrical currents entered the body of the accused. It should not be expected that such evidence is available given that the accused was not involved in a controlled experiment. Dr Ho has previously observed approximately 2500 research tasering of humans.[4] From his academic training and empirical studies he is able to express an opinion from a body of knowledge that is sufficiently organised to be a reliable body of knowledge and experience.
[4] ts 20 (09/04/2025).
As counsel for the accused stated, the absence of any considerable scientific analysis is no doubt, in part, a result of AXON's relatively recent emergence and control over the distribution of tasers to both government enforcement and the military and the statutory restrictions that would ordinarily apply to such weapons as in Australia.[5]
Expertise of Dr Ho/independence - objection
[5] Defence Written Submissions [26].
The State has provided an extensive curriculum vitae of Dr Ho which is produced in the State's brief of evidence.[6] Dr Ho also confirms his qualifications and experience within the body of his expert report. Dr Ho is a practicing, American residency trained and board certified emergency medicine and EMS medicine physician. Dr Ho holds the academic appointment of Professor of Emergency Medicine at the University of Minnesota Medical School. Dr Ho has served as an expert research consultant and medical director to AXON Enterprise, with his particular area of expertise being the physiological effects of tasers upon humans.
[6] Brief of Evidence, pages 449 ‑ 496.
Dr Ho states in his report that he has conducted numerous research studies on the taser devices and has had his work published in peer‑reviewed medical journals and has presented at national/international meetings and assemblies on these topics. Further, Dr Ho states that he has provided expert opinions on taser effects on human subjects in other legal cases in the United States and internationally. Dr Ho has given evidence on one previous occasion in the Coroner's Court of Western Australia concerning the physiological effects of taser use.
I am satisfied that Dr Ho is duly qualified to give his opinion.
Further, the defence submits that there are serious issues regarding the independence of Dr Ho given that he is employed by AXON, the manufacturer of the relevant taser. Dr Ho is the medical director employed by AXON. The defence submits that Dr Ho has an obvious conflict of interest and that his lack of independence renders his opinion inadmissible.
The State's submission is that there is no principle in law that an expert witness be entirely independent of police or prosecuting authorities. This submission is properly made. It is not uncommon that expert witnesses are employed by law enforcement agencies to give evidence in respect to topics such as arson, crash reconstruction, blood pattern analysis and drug investigations. In this particular case, Dr Ho's connection with police is even less direct than other law enforcement officers. However, he does have a professional connection with a company that supplies equipment to Western Australia Police, namely the taser.
The State submits that, relevant to this issue, AXON are not potentially exposed to criticism or censure at the accused's trial. There is no question in this case the taser operated effectively and as it was designed to do, and that it was operated by the deceased within the parameters of applicable use of force guidelines.[7]
[7] Report of Mr Markham (762) at Brief of Evidence, page 270.
I am satisfied that Dr Ho's employment with AXON will not affect his objectivity or the admissibility of his testimony. By his very employment with the manufacturer of the taser he has had extensive experience concerning the effects of a taser on a person. In making this finding, it remains open to counsel for the accused, if he wishes to do so after considering the forensic value to his client's interest, to examine Dr Ho concerning his independence as an expert given his employment with AXON.
The ultimate issue - objection
There are issues that arise in respect to the leading of evidence such as Dr Ho's concerning the ultimate issue. That the defence raises this objection is understandable given that Dr Ho in his written report does at various points state his opinion as to the impact, if any, the taser had on the accused.
The State has submitted in written submissions that it does not 'intend to adduce evidence from Dr Ho as to the actual effect that the tasering had on the accused, which the State accepts is the ultimate issue and a matter for the jury. The State submits that the only person who knows the actual effect the tasering had on the accused is the accused himself'.[8] The State's submission is properly made.
[8] Written Outline of State [18] ‑ [19].
Rather, counsel for the State confirmed in oral submissions that Dr Ho will give evidence concerning the effect of tasering generally. The premise of the questioning will be based on the evidence at trial concerning the nature of the tasering of the accused by the deceased.
The State submits that the evidence is being led so that the jury will be able to consider the explanation given by the accused in his EROI and determine the truth and reliability of his assertions as to the effect that the taser had on him. The accused stated in his EROI that the taser deprived him of bodily control and resulted in the involuntary reversing and movement of the vehicle leading to the death of the deceased.
I accept that the jury will not have direct experience of the effect of a taser on the human body.
The State is able to lead evidence from a relevantly qualified expert as to the effect that a taser would have on muscles that are subject to tasering and what factors are relevant to the effectiveness of any given tasering in terms of its ability to incapacitate and the extent of any incapacitation.
The proposed testimony of Dr Ho, if led in the restricted manner that counsel for the State has confirmed in submissions it intends to lead it, does not amount to the State leading evidence concerning the ultimate issue at trial. The jury will determine whether, on the basis of the entire evidence that they accept, including the testimony of Dr Ho, they are satisfied that the accused intentionally and consciously drove the vehicle into the deceased.
Objection to Dr Ho's opinion regarding relevance of depth of taser
The defence makes an objection to one specific aspect of Dr Ho's proposed testimony, namely the degree of probe penetration.[9] Dr Ho, in his report, refers to the fact that for a taser to have a maximum incapacitating effect it is necessary for the probes to have excellent and continuous contact with their target. In the circumstances of this case, it is more likely than not that the accused did not receive consistent or uninterrupted electrical contact because the probe to the thigh would have had to undergo some degree of arcing to drive the current across an openair gap since it was not fully embedded in the tissue of the thigh. Dr Ho explains the meaning of the phrase 'fully embedded' to indicate a probe that is stuck into human tissue up to the hilt. Dr Ho states that he is unable to say to what depth the probe to the thigh did or did not penetrate.
[9] Report of Dr Ho [12].
The State has confirmed in written submissions that it does not intend to adduce an opinion from Dr Ho as to the depth of penetration of the taser probes in this case.
Rather, it appears that the State will proceed on the basis of asking Dr Ho about the relevance of the depth of a probe generally but that Dr Ho will not be able to make any finding as to the depth of the probe in this particular case. Therefore, his testimony will comprise the relevance of depth and the absence of his ability to make the finding concerning the depth of the probe into the body of the accused.
The defence appears to object to Dr Ho giving general evidence concerning the relevance in any case as to the impact of the depth of the probe on the level of incapacitation. As counsel for the State submitted, in the absence of general evidence concerning the relevance of the depth of the probe, the jury may form the view that the nearest contact between the probes and the human skin or the slightest degree of penetration might result in the full incapacitating effect of a taser charge.
Accordingly, I am satisfied that the State may lead evidence from Dr Ho concerning the relevance of the depth of the probe into the body of a person who is subject to being tasered.
Counsel for the State in submissions stated that whilst there is no direct testimony from any witness concerning the depth of the probe, it would be open for the State to invite the jury to consider photographs that will be produced at trial to determine on the State's case that the puncture wounds were minor and that the probes were not embedded in the tissue of the accused's body. Whether that submission ultimately may be made to the jury, or whether there may be judicial direction concerning any such submission on the basis that the jury is being invited to speculate, can only be determined after the evidence has been received at trial. In the meantime, I am satisfied that the State may lead evidence of the general nature to which counsel for the State proposes to rely.
Exclusion on discretionary basis
The defence submits that the combined effect of the objections regarding admissibility requires that the evidence be ruled inadmissible on the basis that its prejudicial effect outweighs its probative value. A recent statement of the principle of the discretion to exclude is in Le‑Ta v The State of Western Australia:[10]
A trial judge's discretion to exclude admissible evidence where the prejudicial effect of the evidence outweighs its probative value is well established. In this context, it is important to understand what is meant by 'prejudice'. Evidence is not prejudicial simply because it tends to prove the guilt of the accused. Prejudice arises from the risk of improper use of the evidence. Evidence will be prejudicial only when the jury are likely to give the evidence more weight than it deserves or when the nature or content of the evidence may inflame the jury or divert the jurors from their task. As Nettle J has explained, by this discretion, evidence is excluded where and because its capacity to lead a jury to reason correctly to a verdict of guilt is outweighed by its capacity to lead the jury to reason incorrectly to a conclusion of guilt. (footnotes omitted)
[10] Le‑Ta v The State of Western Australia [2020] WASCA 14 [44].
The defence submits that there is a real risk that the jury will give Dr Ho's opinion more weight than it deserves, irrespective of any judicial directions given, due to:
(1)his connection to AXON as its Medical Director and the imprimatur that would entail;
(2)the absence of any robust scientific endeavour or bodies to universally test Dr Ho's ideas and theory; and
(3)the small amount of research (in a relative science context) that has actually been conducted and relied upon by Dr Ho.
After carefully considering the proposed evidence, I find that the prejudicial effect does not outweigh its probative value and therefore, I will not exercise my discretion to exclude the evidence.
Conclusion
Accordingly, I find that the proposed testimony of Dr Ho is admissible.
I certify that the preceding paragraph(s) comprise the reasons for decision of the Supreme Court of Western Australia.
CEM
Associate to the Hon Justice McGrath
10 APRIL 2025
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