R v Wrigley (No 3)

[2025] NSWSC 397

Supreme Court

New South Wales

Medium Neutral Citation:

R v Wrigley (No 3) [2025] NSWSC 397

Hearing dates:

4, 7, 9 and 10 April 2025

Date of orders:

15 and 28 April 2025

Decision date:

28 April 2025

Jurisdiction:

Common Law

Before:

Ierace J

Decision:

(1)    The opinions of Professor Seneviratne as to the probability of the consistency of particular mobile phones being in specified locations, is admissible.

(2)    The opinion of Professor Seneviratne as to the Telstra and Optus mobile phones being in the same specific location at the same time is inadmissible.

Catchwords:

EVIDENCE — Opinion evidence — Exceptions — Expert opinion — telecommunications and cell tower evidence — objection to parts of expert evidence and two expert reports — dispute as to the location of the accused — whether expert was qualified to express an opinion that the antenna that a mobile phone connected with was in fact the closest antenna and cell tower to its location — whether expert was qualified to express an opinion as to whether two mobile phones were in the same specific location

Legislation Cited:

Evidence Act 1995 (NSW), s 79(1)

Cases Cited:

Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588; [2011] HCA 21

Makita (Aust) Pty Ltd v Sprowles (2001) 52 NSWLR 705; [2001] NSWCA 305

Category:

Procedural rulings

Parties:

Rex
Clinton Beau Wrigley (Accused)

Representation:

Counsel:
M Swift (Crown)
N Broadbent SC (Accused)

Solicitors:
Solicitor for Public Prosecutions (Crown)
Legal Aid NSW (Accused)

File Number(s):

2023/101184

JUDGMENT

1. HIS HONOUR: The accused, Clinton Wrigley, is on trial on a count of murder, namely, that on or about 23 January 2023, near Nyngan, he murdered Joel Carter (the deceased). There are three other counts on the indictment, involving the theft and/or disposal of property that was allegedly taken from the deceased’s residence, at about the time of his death.

2. The allegation in the Crown case is that on the evening of 22 and 23 January (all dates in this judgment are for the year 2023, unless otherwise stated), the accused, who was aged 37 at the time, drove to a remote rural property known as Rosehill where the deceased, aged 59, was residing alone, and killed him by inflicting blunt force head injuries. He stole a Toyota HiLux (the HiLux) and some Milwaukee-brand tools that had belonged to the deceased. He destroyed the HiLux by setting fire to it on a backroad in the early hours of the morning of 23 January and later sold some of the tools.

3. The Crown case, other than evidence of alleged admissions made by the accused to others, is circumstantial in nature. The Crown will seek to establish that the accused was in the vicinity of Rosehill at the relevant time by evidence that includes expert forensic evidence as to the whereabouts of two mobile phones that the accused is alleged to have used in the early hours of 23 January, the content of text messages and times of certain calls made between those phones and others and the evidence of a witness who is subject to a non-publication order, and who I will refer to for that reason as witness A.

4. The accused has served a notice of alibi on the Crown, asserting that from about 11.30pm on 22 January to about 8am on 23 January, he was in his vehicle, a Toyota Tarago van (the Tarago) which was parked in a specified area of bushland just outside the township of Nyngan, other than between about 12.30am and 2.30am, when he walked into the Nyngan township and back again.

5. The Crown alleges that on the morning of 23 January, the accused used two mobile phones, which the accused disputes he possessed at that time, to send text messages and make voice calls to witness A and the accused’s partner, Natalie Riley, who resided at Warren. One phone operated on the Telstra cell phone network (the Telstra phone) and the other on the Optus network (the Optus phone). The Crown will seek to establish by evidence of a telecommunications expert, Professor Aruna Seneviratne, that the antennae on cell towers with which the mobile phones connected was consistent with the Crown case as to the whereabouts of the two phones over a period of about five hours on the morning of 23 January, and inconsistent with them being at the alibi location.

6. The accused challenges the admissibility of parts of Professor Seneviratne’s evidence as outlined in his evidence on the voir dire and aspects of two reports by him. The first report is dated 10 February 2025. The second is undated; it was admitted into evidence on 7 April 2025, which was the second of two days of Professor Seneviratne’s evidence on the voir dire. He gave his evidence remotely via audio visual link and was unable to transmit a signed copy to the Crown, but since he adopted the report in his evidence, no objection was taken to its admission into evidence.

7. On 15 April 2025, I made an order that the opinion of Professor Seneviratne as to the probability of a mobile phone being, or not being, in certain locations at particular times was admissible. I have also determined that Professor Seneviratne’s opinion that the Telstra and Optus phones were effectively in the same location at certain times is inadmissible. These are my reasons for those determinations.

8. The defence did not challenge Professor Seneviratne’s claim to have specialised knowledge in the area of mobile telecommunications based on his training, study or experience, which was set out in his first report. Professor Seneviratne is an electronics engineer. He has an honours degree in electronic engineering and a Doctorate of Philosophy in communications systems. He holds various senior positions in research agencies involved in communication technologies and has worked for, and held fellowships with, private telecommunication firms in Australia and overseas.

9. The relevant part of the Crown case, by way of background for the purposes of this voir dire, is as follows.

10. The accused resided in Warren with Ms Riley. He was a truck driver and farm hand. The Crown anticipated that witness A would give evidence to the effect that he worked on the Rosehill property growing crops and agisting sheep, by arrangement with the deceased and his father, Owen Carter, who owned both Rosehill and an adjoining property, named Neeroc. Witness A and the accused preferred to reside at Neeroc while working on Rosehill, sleeping in their vehicles there. The deceased resided at Rosehill by himself.

11. The two properties are about 20 to 25km from Nyngan. To drive from one property to the other using public roads takes about 14 minutes, driving at 50-60kph. There were dirt roads on the properties on which a vehicle could drive from the Rosehill house to where the accused was staying at Neeroc at the same speed in about 10 minutes. To walk that distance across the properties, at 5kph, would take about 1 hour and 36 minutes.

12. On Sunday 22 January, at about 9.16pm, witness A and the accused drove into Nyngan from Neeroc, for dinner and a shower at the BP service station (the BP) and returned to Neeroc. At about 11.30pm, the accused told witness A that he was going to look for a stolen quad bike. He drove off in the Tarago.

13. The following morning, at about 2.30 to 2.35am according to witness A, he was woken by a phone call from the accused, who asked him for directions to Warren from a back road, which witness A provided. I note the Crown case is that witness A was mistaken as to the time of the call; phone records indicate the first call he received on that date from a phone that, in the Crown case, was associated with the accused, was at 3.40am.

14. At about 5.28am, witness A was again woken by a phone call from the accused, who told him that he needed a lift back to Neeroc from the back road from Nyngan to Warren. Witness A then noticed that the Tarago was at Neeroc, parked near witness A’s truck. Witness A left Neeroc at about 5.45am in his vehicle (the Landcruiser) to pick up the accused.

15. The Crown case includes evidence to the effect that at about 5.53am, a driver on the Old Warren Road, between Nyngan and Warren, observed a vehicle off the road to be on fire, with no-one around. It was the Hilux (the HiLux fire site).

16. Witness A searched for the accused unsuccessfully for about 60km along the Warren-Carinda Road, between Nyngan and Warren, thinking that was the road that the accused said he was on. He returned to Neeroc at about 7.10am. His phone was flat, so he recharged it. When he turned it back on, at about 7.33am, he noticed he had three missed calls from the accused. Shortly afterwards, he spoke to the accused, who told him that he was along the Old Warren Road from Nyngan, which was a road not known previously to Witness A. Witness A drove to that road and picked up the accused at about 8.10am, after receiving a message from the accused that he had driven past him. They arrived at Neroc at about 8.34am.

17. On the same day that witness A made his statement to police, he drove with police to a location where he said that he picked up the accused (the pick-up point) and participated in a brief videoed explanation on site, which was about 15km from Nyngan and 12.2km from the Hilux fire site, which was further along that road from Nyngan.

18. The Telstra phone connected to satellite by GPS on two occasions on the Old Warren Road between the pick-up point and the HiLux fire site. The first was at 7.31am about 6km from the HiLux fire site towards Nyngan and the second was at 7.48am about 6.2km from the HiLux fire site towards Nyngan.

19. On the morning of 23 January, between 4.19am and 7.26am, there were eight voice calls and 15 failed voice calls between either the Optus or Telstra phone, and Ms Riley’s phone. As well, Ms Riley’s phone sent texts to the Optus phone at 7.21am (“What road?”) and at 7.26am (“Txt me where”, “I’m comin” and “On my way”).

20. In his first report, Professor Seneviratne stated that he was first retained to advise the police in respect of this matter on 23 January 2025. He recited the request he received from the Officer-in-Charge of the investigation, Detective Sergeant Bradley Gardiner (DS Gardiner), to analyse certain cellular data to achieve the following five goals:

“(a)   Provide technical expertise and explain telecommunications, including base stations, bearings and their correlation.

(b)   Provide technical expertise and explain GPS signals for mobile phones and the tracking capabilities.

(c)   Provide an opinion as the accuracy of GPS location data and Device Location Data collected from mobile phones.

(d)   Provide an opinion as the accuracy of GPS location data and Device Location Data collected from the mobile phones of Clinton Wrigley; [witness A], Natalie Riley and Joel Carter.

(e)   Review the Evidence Summary and maps prepared by NSW Police to confirm the movements of Clinton Wrigley; [witness A], Natalie Riley and Joel Carter between 11:00am on 22 January 2023 and 4:00pm on 23 January 2023.”

21. The evidence summary referred to in (e) was a document composed by DS Gardiner. It included eight opinions by DS Gardiner as to the locations of the accused’s Telstra phone and 15 opinions as to the locations of the accused’s Optus phone at specific times, based on “a review of the mobile telecommunication service” activating a specific antenna on a named cell tower, over a period of approximately 12 hours, from 10.56am on 22 January to 10.42am on 23 January. The mobile’s locations were expressed by DS Gardiner as being “consistent” or “inconsistent” with certain locations, although it was not suggested that DS Gardiner had expertise in the area of telecommunications involving the interpretation of data concerning the possible whereabouts of mobile phones.

22. In his first report, Professor Seneviratne stated that all of DS Gardiner’s opinions as to the locations were accurate. He added the following opinions:

“78.   [The accused’s] Telstra mobile service and [the accused’s] Optus mobile service have similar interactions with the cell towers. Therefore, they can and should be considered as a single entity during the specified period, namely between 11:00[pm] on January 22, 2023, and 4:17[am] on January 23, 2023.

79.   The interactions of [the accused’s] Telstra mobile service and [the accused’s] Optus mobile service indicate that they were not in the Nyngan township or surrounding areas between 10:45pm on 22 January 2023 and 7:48am on 23 January 2023. If the CCTV footage, as outlined in the Summary of Evidence, were made available, it could be used to further strengthen my opinion.

…

81.   The Summary of Evidence regarding the interactions of [witness A] and Riley appears to be accurate. If the CCTV footage, as outlined in the Summary of Evidence, were made available, it could be used to further strengthen my opinion.”

23. An understanding of some basic terminology and a mobile phone’s interaction with the phone company’s equipment, as explained by Professor Seneviratne, is helpful in considering the evidence on the issues for determination. Each phone company has its own cell towers, which are also described as base stations. Antennae are attached to them, pointing in specific directions. A cell tower antenna is the communication point with a mobile phone. The direction in which the relevant antenna on the cell tower is pointing is its “azimuth”, measured in degrees from true north.

24. One source of information as to the use of a mobile phone at a particular time is its “Call Charge Records” (CCRs) and “Reverse Call Charge Records” (RCCRs), which is information provided by the phone company that includes the cell tower and the particular antenna on it that the phone connected with. The phone company’s documentation provides the azimuth for that antenna. Another is the data held by the phone company of all interactions with the phone, including voice calls, data, texts and “handshakes”. This term was explained by Professor Seneviratne as interactions between a mobile phone and a cell tower even when the phone is not being used, provided it is turned on:

“… the reason that there is a need for the communication is that the system needs to know where the device is. So if a call is coming through, it needs to route the call to the device. So the device, if it moves from Nyngan to Tottenham, it needs to know that the call needs to be sent to Tottenham, so it actually sends some information to the cell tower saying, ‘I have come to Tottenham now’. And that is referred to as a handshake.

So it does a handshake with the cell tower to say ‘I’m here’, and the system records it … it happens regularly as you also need to know that you’re still in that vicinity despite you not having any communications happening. So what it does is it sends an update message … if you go to the phone records, you’ll see a thing called LAC and SAC. That's essentially information which is exchanged between the device and the mobile station to make sure that they know where they are.”

25. In his first report, Professor Seneviratne explained how a mobile phone connects with a cell tower and the reasons that it may connect to a particular tower:

“Registration

21.   When a mobile phone switches on (powers up), it goes through a process known as network registration or network attachment. This is achieved by a mobile device tuning to a known frequency and listening.

22.   The mobile device scans the available cellular frequencies and identifies the strongest or most suitable base station to connect to from its service provider, the provider of the sim card. The strength of the signal it receives, quality, and other factors determine the most suitable base station to connect to, similar to what is described below in the handover section.

23.   Once a connection is established, the details of the mobile device and the base station it is connected to, are recorded in the Mobile Switching Centre.

Handover

24.   As a mobile device moves from one location area to another, the current base station it is connected to may not provide the strongest signal. In this case, the mobile device needs to establish a connection with the base station that provides a ‘better signal’. This process is called handover or handoff, where the connection is seamlessly transferred from the current base station to another without interrupting communication.

25.   The decision as to which base station to handover to depends on several factors. The specific criteria and algorithms used in making this decision may vary depending on the mobile network technology and the network operator's implementation. Some of the common factors considered when choosing the target base station to handover to are:

Signal Strength: The signal strength of neighbouring base stations is one of the primary factors considered. The target base station is typically chosen based on which one provides a stronger signal and better quality.

Signal Quality: Apart from signal strength, the quality of the received signal is also considered. This includes factors such as the amount of noise (signal-to-noise ratio), the number of errors (bit error rate), and other indicators of the quality of the signal.

Load Balancing: Network operators strive to balance the traffic load across base stations to optimize network performance. The handover decision may involve considering the current load or congestion level of a base station before handing over a connection.

Coverage Area Overlap: The coverage areas of adjacent base stations may overlap to some extent. The handover decision may take into consideration the degree of overlap and prioritize handover to the base station with the largest coverage overlap to ensure a seamless coverage transition.

Quality of Service (QoS): The target base station’s ability to provide the desired Quality of Service Is an important consideration. QoS parameters can include call drop rates, data transfer rates, and other performance metrics.

Mobility Management: The mobile network keeps track of the movement patterns and behaviour of mobile devices. This information can be utilized to anticipate future handovers and make informed decisions about the target base station.

Network Policies and Operator Priorities: Network operators may have specific policies or priorities for handover decisions. These can be based on factors such as customer preferences, contractual agreements, or specific network optimization strategies.

26.   It is important to note that handover decisions are made by the mobile network infrastructure, rather than being directly controlled by the mobile device itself. The network continuously monitors the signal and quality measurements from mobile devices and makes handover decisions based on the aforementioned factors and algorithms.

27.   The specific algorithms used for handover decisions can be complex and depend on the specific network technology and Implementation. Network operators continuously optimise these algorithms to ensure efficient handover processes and provide a seamless user experience as mobile devices move within the network’s coverage areas.

28.   When a mobile (be that initiating or receiving as described below) is moving within a service area or is experiencing cell congestion (too many calls), then the mobile can request a change over to a different base station to assure continuity of the call. Only the cell ID at the point of the start of the connected call is retained in the CCR. Hence the CCR does not give any information about the possible movement of the initiating or receiving mobiles during a call connection. No records are kept of such movements. Implications of this are described below in the section entitled implications.”

26. In his evidence on the voir dire, Professor Seneviratne identified the material he received from police that informed his opinions. It was the CCR and RCCR records for each relevant phone; data provided by the phone companies known as LBM reports (“Location-Based Monitoring reports), two types of which were “EBM” (Event-Based Monitoring) or “LBS” (Location Based Services), which is the above-described recordings of all contacts between the phone and cell tower antennae including phone calls, sending and receiving texts and handshakes; maps showing the locations of the relevant cell towers of the relevant phone companies and the azimuth of each antenna that engaged with the phones; and some telecommunication coverage maps for the Optus cell towers.

26. Professor Seneviratne also received, in respect of the Optus antennae, information as to range and the angle of reception and transmission of each antenna measured in degrees (the arc), for example, 68 degrees. He explained that he assumed that this meant the antenna’s azimuth was in the middle of that arc; that is, using the same example, the antenna had an area of reception and transmission that was 34 degrees to either side of the azimuth. However, he allowed for the possibility that this was incorrect, and that the measurement referred to the arc range on either side, so that, using the same example, the overall arc would be twice 68 degrees; that is, 136 degrees.

27. Professor Seneviratne referred to matters that may impact on the range of a signal from a cell tower antenna:

“So a telecommunications signal travels a given distance based on a number of things. One, the power with which you transmit, so it’s like if you scream, you put energy into your voice, it goes further. The second thing is it’s the obstacles that are in the path, so if the antenna is pointing to a big building, the antenna gets or the signal gets disrupted or dissipated by the building in front of it. And then there are other events that might disrupt the signal or attenuate or reduce the strength of the signal as it goes from the transmitter towards a receiver, and that could be things like temporary obstacles like big trucks passing through or it could be very heavy downfalls of rain and all sorts of things.”

29. In cross-examination, he identified factors that may cause a mobile phone to connect to a tower that is not the closest to its location:

“Q. That is to say that something which is in the direct line of the azimuth is likely to have a stronger signal strength than something which is toward the exterior boundaries of the arc, is that correct?

A. In general terms it is correct but it is also possible as I mentioned earlier that if the direct line of site has some obstacle a reflected signal might have a higher signal strength than the direct one.

Q. Is that to say that signal strength can also depend on environmental and geographical features, do you agree with that?

A. Absolutely, yes.

Q. That can include the weather, correct?

A. Weather to a, a smaller degree than obstacles that are in the path.

Q. What about the presence of things like dust in the air?

A. Dust in the air would have very little impact.

Q. What about man-made structures?

A. Man-made structures in the direct line of path depends on the material that is used but in general it would have an impact.

Q. Certain materials can have a stronger impact than others is that correct?

A. That is correct.

Q. I take it metal is pretty good at blocking signal, would that be correct?

A. That is correct, yes.

Q. Concrete perhaps a little less so but still pretty good?

A. Yeah.”

30. In cross-examination, Professor Seneviratne was questioned about the reliability of an opinion that a mobile phone that is between two antennae on different cell towers that are pointing towards each other is closer to the one that is identified in the CCR and RCCR records, as was the case with an antenna on a cell tower in the Tottenham area and another on a cell tower in the area of Warren:

“Q. In the absence of range data, it is the case is it not that at least hypothetically a person may be bouncing off, or may be pinging off the Tottenham tower when they are in Warren, do you agree?

A. So it depends on how close to Warren - so the pinging, ping-ponging effect would happen at the boundary of the coverage of Tottenham and Warren. So if I draw for simplicity two circles, one around Tottenham and one around Warren, if there was an interaction, intersection of those circles, at the boundary of the intersections there would be a ping-ponging effect between Warren and Tottenham. But if for example the device was very close to Warren, the probability of it connecting to Tottenham is very low. Similarly, if the device was very close to Tottenham it connecting to Warren would be very small as well.

Q. But that depends, doesn’t it, on a series of different assumptions that you’ve made, including what is happening on the network at the particular time, do you agree?

A. Not on the network per se. So the only reason why you would bounce between two cell towers due to network conditions is due to congestion. So if there was a lot of congestion in Tottenham, it might connect to Warren, and similarly if there was a lot of congestion in Warren, it might connect to Tottenham. So I think given the region, I would think the logical assumption that you would make is network condition would not cause those ping-ponging effects and--

Q. But you don’t have that data, correct?

A. I don’t have that – that’s why I said the logical conclusion.

Q. What about … hypothetically if we’re talking about a person who is somewhere in the middle of Warren and Tottenham?

A. That is definitely possible.”

31. Professor Seneviratne explained that “ping-ponging” meant:

“… if … there is overlap of coverage, and generally if the … mobile device was in that coverage area, it is possible that - it is likely that it will ping pong because it will receive the same signal strength from both towers.”

32. For the purposes of preparing his report, Professor Seneviratne was provided with tables of the results of sample measurements of the signal over a range of distances from particular cell-tower antennae. These tables typically had a higher number of successful samples in the mid-range of the entries for the antenna. Professor Seneviratne explained in evidence in chief that the table did not give information as to signal strength or range, although in cross-examination he conceded that it had some utility in that regard:

“Q. Now, you said before that this data doesn’t tell you anything about the particular range of the tower because it's based on samples, is that correct?

A. So, this is samples taken probably on a single day, so it - essentially the only thing you can glean from these measurement reports is that there were more samples in a particular range, therefore you can be very confident that there was coverage up to that range. So for example you can say in the case of Tottenham you could get coverage up to 30,108 (metres) because there were more samples that could be collected and the percentage distribution was 75%. So you can say with a high probability that if the device was up to a range of 30,108 metres it would have coverage from Tottenham.

Q. But it also demonstrates doesn’t it that it’s possible to obtain coverage up to 76,908 metres, do you agree?

A. Yeah it is possible, that is the fringe zone that we were - I was talking about if you drew two circles, if there was overlap that would be in that fringe that I’m talking about.”

33. Professor Seneviratne said:

“So my opinions are primarily based on the azimuth of the antenna, and the coverage maps I was provided was essentially displaying an arc, that’s the funnel that we were talking about. I basically used those to get a bearing of the geography of the places that were being referred to like Neeroc or Rosehill. I had no idea where it was so when, when it said it could not be in Rosehill, I sort of looked at the directional direction of the antenna and said it’s pointing away from Rosehill, therefore it could not - the person could not be in Rosehill area, …”

34. Professor Seneviratne said:

“I relied on the CCR, RCR records that comes from the devices interacting with the base station, as well as LBM or EBM records which are essentially, I guess, charge records that the telecommunications company provided. The other information I relied on was the maps which give the azimuth in the form of arrow, and the accompanying text which says what the azimuth was, so I could verify and say if it said azimuth of 90 of the point ‑ thar row was pointing at 90 degrees. That was the primary information that I used.”

35. Professor Seneviratne’s opinion as to consistency and inconsistency included assumptions as to signal strength. He dismissed a concern that the signal strength may be affected by maintenance being done, because in that circumstance he would expect the signal to not be operating at all.

36. In his second report, Professor Seneviratne gave a further explanation of the process he applied in formulating his pinions in his first report. As to his opinion that the Telstra and Optus phones should be considered as a “single entity” between 11pm on 22 January and 4.17am on 23 January, he explained that it was based on the two phones repeatedly connecting to their respective towers in the same geographical area between those times.

37. In his second report, Professor Seneviratne responded to a request to provide an opinion as to consistency or otherwise of the two mobile phones being in the area identified in the accused’s alibi notice. He explained his methodology and concluded that the device interactions for the two mobile phones were inconsistent with them being in the areas and at the times identified in the alibi notice.

38. In his evidence on the voir dire, Professor Seneviratne tended to express his opinion as to the area in which a mobile phone was or was not, in terms of it being “likely” or “unlikely” to be in that area. He was asked what he meant by concluding that a mobile phone was “likely” to be in a particular area:

“Q. What kind of probability is the word ‘likely’ when you say that?

A. The only thing I can say is that it is highly probable that it is - I can’t give you whether it’s 90% or 80% but it is more than 50% and it’s more, more likely to be in the higher end of percentage range.

Q. So you would choose the word ‘highly probable’ to go in - - -

A. Yeah.

Q. - - - as perhaps a more specific version of ‘likely’?

A. That’s correct yes.”

Submissions of the defence

39. The accused’s objected to the admissibility of the opinions of Professor Seneviratne as to the following: the range, arc and/or mobile reception coverage of each tower on 22 and 23 January; as to whether the locations of the mobile phones were consistent or inconsistent with them being at a particular place; and whether the Telstra and Optus mobile phones have “similar interactions” with their respective cell towers, so that they could be considered to be in approximately the same location as each other.

40. For the purposes of the voir dire, the accused was content to proceed on the basis that the azimuth data of the relevant antennae was correct for 22 and 23 January, although he contended that there was some doubt as to that.

41. Essentially, the defence submitted that the location of the cell tower with which a mobile phone interacts provides little, if any, useful information as to the location of the mobile phone and is apt to mislead if considered in isolation. Sampling of the Optus cell tower antennae demonstrated that some had a range of up to 76km which contributed to the possibility that the Optus phone may not have ben connecting to the closest tower.

Determination

42. There was no dispute, at least for the purposes of the voir dire, that both phone company’s data includes the identification of the particular antenna, and thus the cell tower, with which their mobile phone connected on each occasion that it made contact; whether for a handshake, text message, data transfer or voice message or voice call. There is also no dispute that at the relevant time the mobile phone was in a direction that is consistent with the relevant arc (whether known or not), if not the azimuth itself, of that antenna. That is because these matters are determined from working backwards from the CCR and RCCR data as to what antenna the mobile phone in question did connect with.

43. The accused conceded that Professor Seneviratne is qualified to express opinions as to the location of the relevant cell towers, the azimuth of the connecting antenna for each interaction and the probability (expressed as “likely”, “unlikely”, or “very unlikely”) of a response by a mobile phone that is within or without the direction of the antenna. As to the Optus phone, he could give an opinion as to the range and the size of the arc.

44. Having regard to s 79(1) of the Evidence Act 1995 (NSW), I am satisfied on the balance of probabilities that Professor Seneviratne is qualified to express opinions on those matters, based wholly or substantially on his specialised knowledge.

45. The issue in dispute is whether, having regard to the extent of the available data, Professor Seneviratne is qualified to express an opinion as to the probability that the antenna that a mobile phone connected with was the closest antenna and cell tower to its location, or whether there could have been a closer one that it did not connect with, due to the variables discussed above, such as call congestion, obstacles and the like.

46. The basis of Professor Seneviratne’s opinions include assumptions that may or may not be correct, such as whether there was an obstacle blocking reception with, or call congestion on, a closer tower antenna that the mobile phone was otherwise able to connect with but, due to the algorithms programmed by that phone company, the connection was made instead with a cell tower antenna that was further away but happened to be operating in approximately the same direction as the first tower.

47. This scenario, in isolation, would suggest that Professor Seneviratne’s specialised knowledge did not better place him than someone without that knowledge to form an opinion as to whether the connecting cell tower was in fact the closest with that connective capacity. However, he explained that he took other material into account in forming his opinion, in particular, the data provided by the phone companies of all connections with the mobile phone in the relevant period. This enabled him to determine whether a connection was likely to be with the closest tower antenna or not, in broad characterisations of likely, very unlikely or likely. Professor Seneviratne’s process of reasoning was transparent, in that he was able to explain what data he took into account in arriving at an opinion as to the likelihood or unlikelihood of a phone being in a location at a particular time.

48. Accordingly, Professor Seneviratne’s opinions as to the mobile phone date being consistent or not with certain locations are substantially based on his specialised knowledge. In my view, these opinions come within the ambit expressed in Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588; [2011] HCA 21 by the majority at [37]:

“The admissibility of opinion evidence is to be determined by application of the requirements of the Evidence Act rather than by any attempt to parse and analyse particular statements in decided cases divorced from the context in which those statements were made. Accepting that to be so, it remains useful to record that it is ordinarily the case, as Heydon JA said in Makita,[1] that ‘the expert’s evidence must explain how the field of ‘specialised knowledge’ in which the witness is expert by reason of ‘training, study or experience’, and on which the opinion is ‘wholly or substantially based’, applies to the facts assumed or observed so as to produce the opinion propounded’.’”

1. Makita (Aust) Pty Ltd v Sprowles (2001) 52 NSWLR 705 at 744 [85].

49. However, I am not satisfied that Professor Seneviratne’s specialised knowledge allows him to express the opinion that the Telstra and Optus mobile phones were, as expressed in paragraph (a) of his first report as extracted at [20] above, a “single entity”; that is, that they were effectively at the same precise locations. The evidence on the voir dire did not satisfy me that Professor Seneviratne’s opinion was, in fact, based wholly or substantially on his specialised knowledge. Rather, I am of the view that it is speculative.

Orders

50. I made order (1) as follows on 15 April 2025 and now add order (2):

1. The opinions of Professor Seneviratne as to the probability of the consistency of particular mobile phones being in specified locations, is admissible.

2. The opinion of Professor Seneviratne as to the Telstra and Optus mobile phones being in the same specific location at the same time is inadmissible.

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Endnote

Decision last updated: 03 June 2025