Citation: R v Chandler [2014] NSWDC 148
Court: District Court of New South Wales
Date: 26 August 2014
Judge(s): S Norrish QC
Background
The accused was charged in connection with a robbery. A knife found several streets from the scene, embedded in a mattress near items taken from the victim's wallet, was submitted for forensic DNA analysis by the NSW Forensic and Analytical Science Service (FASS).
Forensic analysis identified a partial DNA profile on the blade of the knife, which matched the victim's profile. This testing used the "Promega Powerplex 21" system, a newer and more sensitive method than its predecessor, introduced nationally in early 2013. A separate analysis of the knife's handle produced results consistent with the accused's DNA profile, and no objection was ultimately pressed in relation to that evidence.
The defence objected to the admissibility of the opinion evidence of Vivienne Beilby, a Senior Forensic Biologist at FASS, concerning the blade sample. A voir dire was conducted to determine whether that evidence was admissible.
Legal Issues
- Whether Ms Beilby's opinion evidence was admissible under s 79 of the Evidence Act 1995 as a recognised exception to the opinion rule
- Whether the factual basis and reasoning underlying Ms Beilby's opinions were sufficiently disclosed in her reports and supporting materials
- Whether the probative value of the evidence outweighed any danger of unfair prejudice under ss 135 and 137 of the Evidence Act 1995
Decision
Issue 1: Disclosure of the basis for the expert opinion
The court found that Ms Beilby's initial certificates and supporting statements did not adequately reveal the factual assumptions underpinning her opinion, nor did they identify the matters she took into account in reaching her conclusions. This was a significant deficiency, and the court noted that information Ms Beilby had provided to the Crown prosecutor in conference should have been disclosed to the defence and, where necessary, to the court itself.
Issue 2: Sufficiency of basis following the voir dire
During the voir dire, additional statements and laboratory working documents were produced by the prosecution. Ms Beilby also gave oral evidence explaining the "markers" identified at particular loci of the DNA profiles, represented as spikes in graphs. The court found that, taken together, this material provided the basis for her opinion of a partial match between the blade sample and the victim's profile. The matching itself, once the working documents were explained, was described as self-evident.
Issue 3: Statistical probability and reliability of the Powerplex 21 system
The court accepted Ms Beilby's evidence as to the statistical methodology used to calculate the probability of the identified DNA profile occurring in the Australian population (fewer than one in one hundred billion). No evidence was advanced suggesting the Powerplex 21 system or the method of calculating frequency was unsound or unreliable. A defence expert, Ms Jae Gerhardt, raised concerns about the character of the sample and low DNA levels, but did not challenge the reliability of the data produced by the Powerplex 21 system itself.
Issue 4: Admissibility and prejudice
The court concluded that Ms Beilby's evidence was relevant and admissible under s 79 of the Evidence Act 1995. Its probative value outweighed any danger of unfair prejudice, and no specific unfair prejudice had been identified in submissions. The court noted that appropriate warnings would be given to the jury in due course.
Orders Made
- Evidence is admissible
Key Takeaways
- Under s 79 of the Evidence Act 1995, expert opinion evidence must disclose the factual assumptions and reasoning upon which it is based. Initial certificates and reports that leave significant gaps may be found deficient, even if those gaps are later remedied through additional statements and oral evidence during a voir dire.
- Information provided by an expert witness to the prosecution in conference, where it explains or fills gaps in documentary evidence, ought to be disclosed to the defence and, where necessary, to the court.
- The District Court confirmed that the admissibility of DNA opinion evidence based on the Powerplex 21 system was not undermined where no evidence was advanced to suggest the system, or the statistical method applied to it, was unreliable or unsound.
- A defence expert's concerns about sample quality and low DNA levels did not displace admissibility where those concerns did not go to the reliability of the underlying data generated by the testing system.
- Applying Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705 and R v Sing (2002) 54 NSWLR 31, the court assessed whether the reasoning chain of the expert was sufficiently exposed. Once the working documents were explained through oral evidence, the court was satisfied the necessary foundation had been established.
Legislation and Cases Referenced
Legislation
- Evidence Act 1995
Cases
- Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705
- R v Sing (2002) 54 NSWLR 31
- Keller v R [2006] NSWCCA 204
- Sharwood v R [2006] NSWCCA 157