In Canada, lawyers are barred from using fraudulent means to mislead a court. Lawyers are also barred from permitting a witness to be presented in a false or misleading way. However, neither Canadian law nor Canadian professional codes clarify the permissibility of challenging a Crown witness with truthful evidence when defence counsel knows that the accused is guilty. This article explores the lack of guidance across the Canadian legal profession, and then uses Canadian and American legal scholarship to identify different approaches put forward on this topic. It concludes that there should not be an absolute ban on the practice of counsel for guilty accused used truthful evidence to challenge a Crown witness. Defence counsel must ensure convictions are only obtained by sufficient reliable evidence. Defense must also help clients obtain any remedy and defence not prohibited by law. However, a contextual approach should be taken in determining if the practice is appropriate and ethical in each case. This approach would consider, for example, the circumstances of the case, intended use of the evidence, legal merit to the claim it is used in support of, harm to the respective witness, and impact on justice norms such as equality, anti-discrimination and harm reduction.
Jeremy Tatum, "Navigating the Fine Line of Criminal Advocacy: Using Truthful Evidence to Discredit Truthful Testimony", online: (2012) 2:2 UWO J Leg Stud 2 <http://ir.lib.uwo.ca/uwojls/vol2/iss2/2>.