Convicted murderer Scott Watson's application to include an academic report on eyewitness memory in his upcoming appeal has been thrown out by the court.
Watson was found guilty of murdering Ben Smart and Olivia Hope after they disappeared during New Year's Eve celebrations in Marlborough Sounds in 1998.
He was sentenced to life imprisonment with a minimum period non-parole period of 17 years.
Watson has always maintained his innocence. A Court of Appeal bid against his convictions was dismissed in 2000 and the Privy Council declined to grant Watson special leave for Watson to appeal in 2003.
An application to the governor-general for exercise of the Royal prerogative of mercy was declined in 2013, but succeeded on a second attempt in 2017.
In 2020, then governor-general Dame Patsy Reddy referred Watson's case back to the Court of Appeal after reports from a forensic scientist questioned the reliability of the hair evidence. The appeal will be heard in June.
One of the grounds of appeal is that the photographic procedure through which Watson was identified did not produce a reliable identification, and therefore should have been inadmissible.
His legal team have produced evidence from two experts on eyewitness identification evidence, Dr Gary Wells and Dr Adele Quigley-McBride, who supported the submission that the identification evidence was unreliable and its admission gave rise to a miscarriage of justice.
The Crown engaged psychology professor Dr Margaret Bull Kovera to prepare a report on the psychological research on eyewitness memory.
The Crown said it sought evidence from an academic "who works in broadly the same US academic milieu" as Watson's visual identification experts, Drs Wells and Quigley-McBride, who will be cross-examined at the hearing.
Watson's lawyer Nick Chisnall said it was in the interests of justice to include the report, which he described as "fresh, credible and cogent", which would assist the court in determining the appeal.
Chisnall said Dr Kovera had reached the same conclusion as Drs Wells and Quigly-McBride, that the identification evidence was unreliable.
He said "suppressing" the report was not consistent with the Crown's duties as a model litigant to act in a fair, detached and objective manner.
Crown prosecutor Madeleine Laracy said Dr Kovera's evidence aligned with Watson's expert evidence, it did not offer materially different conclusions and did not fill a critical evidential gap.
The report had been provided to Watson and under the ordinary fresh evidence procedures Watson could call Dr Kovera himself.
The Court of Appeal ruled that producing the report was not "necessary or expedient" in the interests of justice, or for determining the appeal.