Thanks to Barb Legate for this comment on our post on McNeill v. Filthaut, regarding the current debate over the testimony of accident benefits assessors:
"A point that seems to be missed in some of these analyses is that notwithstanding the provisions of Rules 4 and 53, those rules are merely a codification of the law that stated with Amertek. Rules 4 and 53 are part of the Mohan criteria, and fall under the "any exclusionary rule" branch. So, although there are exclusionary rules for experts a party retains, that does not end the analysis. If a witness is to give opinion evidence, the witness has to be qualified as an expert. Part of the qualification exercise is to enquire into bias. Bias also enters into the relevance assessment. See CA decision in Abbey.
IMHO, those cases that strain to differentiate treating opinions from AB opinions from DAC opinions and retained expert opinions have missed the basic law: you want to call a witness to give an opinion, then follow Mohan. No fancy differentiations needed."