The D.A.I. case involved a mentally challenged 23-year-old complainant who alleged that her mother’s common law partner had repeatedly sexually assaulted her over a period of four years. The complainant’s mental capacities were found to be equivalent to those of a three- to six-year-old child and the trial judge excluded her evidence because it had not been shown that she understood the duty to testify truthfully.
The lack of evidence from the complainant resulted in the acquittal of the accused, which was subsequently upheld by the Ontario Court of Appeal. On further appeal, the Supreme Court of Canada had to consider whether the exclusion of the complainant’s evidence was appropriate. Chief Justice McLachlin, writing for the majority of the court, stated that the Charter of Rights and Freedoms “guarantees a fair trial to everyone charged with a crime”, and described the question at hand as follows:
The question is this: does allowing an adult witness with mental disabilities to testify when the witness can communicate the evidence and promises to tell the truth render a trial unfair?
The answer to this question, in the majority’s opinion, is no. Chief Justice McLachlin justified this conclusion as follows:
The requirement that the witness be able to communicate the evidence and promise to tell the truth satisfies the low threshold for competence in cases such as this. Once the witness is allowed to testify, the ultimate protection of the accused’s right to a fair trial lies in the rules governing admissibility of evidence and in the judge or jury’s duty to carefully assess and weigh the evidence presented. Together, these additional safeguards offer ample protection against the risk of wrongful conviction.
D.A.I.’s acquittal was set aside and a new trial ordered. The decision was not unanimous, however, with Justices Binnie, Lebel, and Fish dissenting.
Decided by the Supreme Court of Canada on February 10, 2012.
Click here for the full text of the decision.