News Item

July 2020

Research Report Evaluates use of Expert Evidence about Memory and its relevance to Sexual Violence Cases in NZ

The report by psychologists Suzanne Blackwell and Fred Seymour, and lawyer Sarah Mandeno examines evidence given by memory expert witnesses in sexual violence trials and appellate courts in New Zealand. In Part One their report provides an overview of legislation and case law relating to the admissibility of expert evidence. It also overviews The Code of Conduct for Expert Witnesses that provides guidance for those giving expert evidence. Part Two of the report is dedicated to summarising opinions given by memory expert witnesses and describing the studies they cite in support.

The project arose out of increasing concern that the nature of memory expert evidence offered to the courts seemed to focus on portraying the memories of complainants and other prosecution witnesses as essentially flawed.

With regard to admissibility of memory expert evidence the authors state that there has been an increase in applications to admit memory evidence in sexual violence cases over the last two decades, most commonly by defence counsel, and most frequently where allegations are of historical child sexual abuse. Memory expert evidence has been admitted in some cases but deemed inadmissible in others. Thus, memory expert evidence may be regarded as contentious in our courts – as it is in courts in similar commonwealth jurisdictions. At issue is whether jurors need educating about memory, whether the memory evidence offered represents settled science and/or whether memory witnesses inappropriately offer opinion about the credibility of witnesses. With regard to the memory expert evidence that has been offered, the authors have become increasingly concerned that research cited in support of opinions expressed in the briefs of evidence of memory expert witnesses, exaggerates memory fallibility in relation to sexual violence complaints. They argue that much of the research cited had limited relevance or ecological validity to the issues inherent in sexual violence trials.

Research findings raised a number of concerns regarding expert memory evidence presented in sexual violence cases:

  • A wide range of topics covered in the briefs of evidence were included routinely regardless of the facts of a given case
  • Expert memory evidence speculated the complainant had been subjected to post-event misinformation but there was no evidence at trials that indicated this was the case
  • Research cited in support of expert memory evidence included studies/experiments far removed from actual experience of sexual violence
  • Briefs of evidence provided none of the caveats contained in research papers cited by the memory expert witnesses giving evidence

The researchers found expert memory evidence often failed to meet the standards required by the Code of Conduct for Expert Witnesses regarding relevance and balance. In their opinion this has potential to obstruct access to justice for complainants of sexual violence.

The report considers the implications for victims/survivors of sexual violence and child sexual abuse should such memory evidence become more widely accepted in our courts. It notes that complainants are already routinely challenged as to the truth of their allegations – memory expert evidence of the sort offered to date creates further challenges.

Researchers Suzanne Blackwell and Fred Seymour have extensive experience as clinical psychologist practitioners working with child and adult victim survivors of sexual abuse, and their families, and extensive experience working with offenders. They have often been engaged by the Crown as expert witnesses to give educative evidence in sexual violence trials. They have also provided expert reports for defence counsel. Sarah Mandeno is a lawyer who has worked both as prosecuting and defence counsel.

Research Report Expert Evidence about Memory in New Zealand Sexual Violence Trials and Appellate Courts 2001 to 2020 – PDF, 154 pages

The Law Foundation and the Borrin Foundation have provided $52,500 in support of this research