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Supreme Court 5 May 2023

R v Niguidula (No 2)

[2023] NSWSC 476

Homicide
CRIMINAL PROCEDURE EVIDENCE EXPERT EVIDENCE VOIR DIRE EXPERT REPORT OBJECTION EVIDENCE

Citation: R v Niguidula (No 2) [2023] NSWSC 476
Court: Supreme Court of New South Wales
Date: 5 May 2023
Judge(s): Dhanji J

Background

The accused faced two counts: assault occasioning actual bodily harm and the murder of the deceased, who died from a single stab wound to the chest. A central factual dispute at trial was whether the wound was inflicted by the accused or was self-inflicted by the deceased. The trial was scheduled to commence on 9 May 2023.

The Crown proposed to call Professor Duflou, a well-known forensic pathologist, to give expert evidence on that question. His first report of 13 April 2023 described the wound characteristics, the autopsy findings, the absence of hesitation marks and defence injuries, and included a concluding paragraph expressing his opinion on the likely cause.

The accused did not object to the bulk of Professor Duflou's proposed evidence but objected specifically to the final paragraph of his report, in which he concluded that it was "much more likely" the stab wound resulted from an assailant than from self-infliction. That objection came before Dhanji J on a voir dire (a pre-trial hearing to determine the admissibility of evidence).

  • Whether the concluding paragraph of Professor Duflou's report constituted admissible opinion evidence under s 79(1) of the Evidence Act 1995 (NSW), specifically whether the opinion was "wholly or substantially based" on specialised knowledge derived from his training, study or experience.
  • If s 79(1) was satisfied, whether the evidence should nonetheless be excluded under s 137 of the Evidence Act on the basis that its probative value was outweighed by the danger of unfair prejudice.

Decision

Dhanji J upheld the objection and ruled the final paragraph of Professor Duflou's report inadmissible. The core difficulty was not Professor Duflou's qualifications, which were accepted, but the adequacy of the link between his specialised knowledge and the opinion expressed in that paragraph.

The court applied the well-established test from Dasreef and Makita: an expert's opinion must explain how the field of specialised knowledge applies to the observed or assumed facts so as to produce the opinion. In the critical section of his report titled "differentiating self-inflicted from inflicted sharp force injuries," Professor Duflou described the factors relevant to such assessments at a general level, but his report did not sufficiently demonstrate how his expertise, as distinct from ordinary logical reasoning, drove the ultimate conclusion that an assailant was "much more likely" responsible.

Dhanji J was not satisfied on the balance of probabilities, as required by s 142 of the Evidence Act, that the conclusion was substantially based on Professor Duflou's specialised knowledge. The court could not identify a transparent process of reasoning that connected his expertise to the final opinion expressed.

Although it was unnecessary to decide the s 137 question given that conclusion, Dhanji J noted significant reservations about allowing the paragraph before the jury in any event. The expression "much more likely" was imprecise, and the risk was that the jury would simply adopt the authoritative conclusion of a highly qualified expert rather than independently evaluating the underlying factors. The court expressed a preference for the jury to understand and weigh those individual factors themselves.

Orders Made

• The objection to paragraph [24] of the report of Professor Duflou of 13 April 2023 is upheld.

Key Takeaways

  • Under s 79(1) of the Evidence Act 1995 (NSW), an expert opinion must be wholly or substantially based on specialised knowledge. Demonstrating that a witness has relevant qualifications is necessary but not sufficient. The report must also show how that specialised knowledge was applied to the facts to produce the opinion.

  • A conclusion framed in terms of likelihood ("much more likely") does not automatically satisfy the s 79(1) gateway if the reasoning process connecting the expert's specialised knowledge to that conclusion is opaque or indistinguishable from ordinary logic.

  • The court applied the standard of proof in s 142 of the Evidence Act, requiring the party seeking admission of the evidence to satisfy the court on the balance of probabilities that the admissibility condition was met.

  • Even where the s 79(1) threshold might be met, imprecise probabilistic language in an expert opinion can give rise to serious s 137 concerns, particularly where the jury may defer to the expert's authority rather than independently assess the underlying factors.

  • The decision reaffirms the principles from Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588 and Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705 that admissibility is determined by faithful application of the Evidence Act requirements, not by credentials alone.

Legislation and Cases Referenced

Legislation
- Evidence Act 1995 (NSW), ss 76, 79(1), 137, 142

Cases
- Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588; [2011] HCA 21
- Honeysett v The Queen (2014) 253 CLR 122; [2014] HCA 29
- Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705; [2001] NSWCA 305
- R v Warwick (No 37) [2019] NSWSC 196
- HG v The Queen (1999) 197 CLR 414; [1999] HCA 2 (referenced within cited authorities)
- Daubert v Merrell Dow Pharmaceuticals Inc (referenced within cited authorities)