Ben Smart and Olivia Hope, left, and Scott Watson. Photo: SUPPLIED / Pool / John Kirk-Anderson
The Court of Appeal has ruled lawyers for the man convicted of murdering Ben Smart and Olivia Hope can include extra expert evidence in his appeal next year.
The two young people disappeared during New Year's celebrations in Marlborough Sounds in 1998. Scott Watson has long claimed his innocence and is set to launch his latest appeal in June.
At a hearing last month, Crown lawyer Madeleine Laracy argued Watson's legal team needed to explain why they should be allowed to include two new expert reports about hairs, thought to belong to Hope, found on a blanket on Watson's yacht Blade.
Watson's lawyer Nick Chisnall argued the full hearing panel would be better placed to decide on their relevance.
In a decision released on Monday the Court of Appeal agreed.
"It is, at this stage, extremely difficult to assess the cogency of [the] evidence. The panel which hears Mr Watson's appeal will be in a far better position to assess what, if any, cogency attaches to the challenged evidence after it considers all other relevant evidence," the decision said, noting Laracy had accepted the Court would have difficulty ruling on admissibility without knowing what other the evidence would be covered at the appeal.
"The Crown's application to exclude the evidence can be pursued at the appeal if necessary."
One report, by a forensic scientist with 20 years' experience, focused on the 1998 procedures for examining hair and DNA samples, and whether those procedures aligned with international guidelines, the court ruling said.
It suggested the steps taken when obtaining the hairs did not conform with ESR standards and the failure to separate samples may have increased the risk of contamination. The report looked at the examiner not changing her lab coat between examinations, and what procedures were followed after she made small cuts in the plastic bag containing the hairs.
The second report, by a crime scene investigator with 25 years' experience, discussed how the ESR scientist secured the blanket and the process of documenting the steps taken by the scientist examining the yacht.
The case was referred back to the Court of Appeal in 2020 by then governor-general Dame Patsy Reddy, after reports from a forensic scientist called into question the reliability of the hairs. This latest ruling found the reports could help the Court understand the establishment and evolution of procedures designed to prevent or minimise contamination.
"This is an issue raised by the reference from the Governor-General and the expert evidence on this topic complements other evidence relating to whether or not there was contamination," it said.
"We cannot at this juncture say that the reports ... will not substantially assist this Court in understanding the evidence in the case, or in determining whether or not there was a substantial risk that the hair samples seized from the Blade were contaminated either at the time they were located or when they were examined in a laboratory."