Expert evidence or expert decisions? Measuring the impact of expert evidence on criminal proceedings outcomes in the Provincial Court of Manitoba

Abstract

Expert evidence is an integral part of the Canadian justice system, however its use comes with inherent risks. Improperly utilized, expert evidence can lead to serious injustices, such as wrongful convictions. This has been a recurring problem throughout Canadian legal history, and on which is often only identified after injustice has occurred. This study examines all reported Criminal decisions and admissibility rulings from the Provincial Court of Manitoba and compares success rates in cases without expert evidence to those where expert evidence was led to determine how the presence of expert evidence influences outcomes. It is argued that the presence of a significant positive gap between success rates with expert evidence and the base rates may be an indicator that safeguards against dubious expert evidence are ineffective. This study ultimately finds that such a positive gap does appear where the Crown leads expert evidence. The results for the defense are less clear. It is argued that this pattern is concerning, that further investigation into this needs to be done, and that existing safeguards need to be strengthened.