Watson v The King

In the case of Watson v The King, the legal dispute centres around the admissibility of expert opinion evidence in relation to the potential contamination of crime scene hair samples. The matter was brought before the court by the defendant, Watson, who sought to challenge the validity of the evidence used against him in his criminal trial. The court was required to determine whether the expert opinions of Ms Crawford and Ms Thirkell on the procedures designed to prevent or minimise contamination of crime scene samples were admissible and substantially helpful in understanding the evidence and ascertaining facts relevant to the appeal. The Crown argued that the evidence was not fresh and could have been obtained for the trial with reasonable diligence. The court found that the expert evidence was admissible as it was likely to provide substantial assistance in understanding the procedures in place to prevent contamination and in determining whether there was a substantial risk of contamination of the hair samples in question.

The court examined the admissibility of the expert evidence under section 25(1) of the Evidence Act, which requires that expert opinion evidence be substantially helpful in understanding other evidence or ascertaining facts of consequence to the proceeding. The court considered that the expert evidence in this case was intended to help understand the procedures designed to prevent or minimise contamination, an issue raised by the reference from the Governor-General. While the test for admissibility of expert opinion is higher than that for other evidence under section 7(3) of the Evidence Act, the court found that the expert reports from Ms Crawford and Ms Thirkell could substantially assist in understanding the evidence in the case and in determining whether there was a substantial risk of contamination of the hair samples. The court also considered the Crown's argument that the evidence was not fresh and could have been obtained for the trial with reasonable diligence. However, the court found that the overall interests of justice trumped issues of freshness, and the strength and potential impact of the evidence on the safety of the conviction were factors to be considered in determining admissibility.