The expert witness’s duty of impartiality in Canada

Abstract

In this case note, the authors review a recent decision of the Supreme Court of Canada in which the Court tightened the admissibility requirements of expert witnesses. The Supreme Court confirmed that expert witnesses owe a special duty of impartiality at common law to provide ‘fair, objective and non-partisan assistance’ to the trier of fact. On the question of admissibility, the Supreme Court adopted an approach broadly consistent with England by imposing a threshold eligibility requirement for the admission of expert evidence. An expert will be qualified to testify only if he or she is aware of and willing to carry out their duty of impartiality to the court. In addition, the trier of fact continues to act as a gatekeeper by assessing the probative value of the proposed expert's evidence and weighing it against the potential for prejudice. Only where the probative value exceeds the potential for prejudice will it be admitted. If the evidence of an expert witness is admitted, less serious concerns about the impartiality of the expert witness can inform the weight accorded to the evidence. The authors conclude that the Supreme Court's decision is a welcome development in Canadian law as it establishes a clear test designed to better safeguard the integrity of the trial process.