Intellectual Disability Considered in Court of Appeal

The case of R v Slatter, 2020 ONCA 807 involved an alleged sexual assault of a complainant who suffered from intellectual developmental disabilities. An expert testified at trial that she was “suggestible”. Despite that, the trial judge still found truth in her evidence and convicted Mr. Slatter.

Upon appeal, the Ontario Court of Appeal instead ordered a new trial on the basis that the trial judge did not consider evidence of the complainant’s suggestibility (among other secondary issues).

The evidence of the expert, a forensic clinical psychologist, indicated that a person with an intellectual disability, such as that of the complainant, may acquiesce and give a desired answer in response to questioning. In other words, they are likely to agree to suggestions made. This expert reviewed the police interview and observed such instances of being led in questioning and changing her answers accordingly. There were times though that her answer did stay the same. This was explained by the expert as depending on the questions posed and amount of pressure applied in asking them.

This issue goes to a witness’ reliability which means the accuracy of their ability to observe, recall, and recount events. The issue was that the trial judge focused mainly on the complainant’s credibility or honesty as a witness without considering her reliability given the evidence presented that she was suggestible. As a result, the appeal was allowed, and a new trial ordered.

The Crown then appealed to the Supreme Court of Canada. The Supreme Court of Canada ruled that when assessing the testimony of a witness with an intellectual or developmental disability, “courts should be wary of preferring expert evidence that attributes general characteristics to that individual” rather than their actual capacities in perceiving, recalling, and recounting. The Court is concerned that applying such general characteristics to witnesses will perpetuate myths and stereotypes about individuals with disabilities which hinders the truth seeking process of the Court and can create barriers for those with disabilities to have access to justice. As a result, the Court restored Mr. Slatter’s conviction.


While the Supreme Court of Canada had the right intention in ensuring not everyone with a disability is painted with the same brush and it recognizes there are differences in abilities to perceive situations, remember them, and communicate what happened; there is some concern that this may lead Courts or counsel to ignore the fact that there are certain common effects from certain disabilities and may inadvertently serve to diminish the experiences of those who may have such disabilities. Caution should be had in not recognizing or appreciating how an intellectual disability may affect someone, even despite the fact they may appear fully functional. Intellectual and developmental disabilities are often invisible and not apparent on the surface and grave error can be had without receiving evidence from an expert and appreciating how they are impacted. That being said, of course any expert testimony ought to be thoroughly tested to ensure their assessment is unique and focused on the individual and how it actually applies to them specifically, as opposed to simply describing the disability generally. In this case, it appears the expert had a strong understanding and made it clear how the complainant personally was affected by this disability, not merely how most people are affected. Overall, what is common between both Courts decisions/rulings and the important takeaway is the need to consider how a disability can impact one’s ability to testify credibly and reliably.