Does the “ultimate issue rule” apply to expert opinion evidence?

Furthermore, the “ultimate issue rule” no longer applies in regards to lay opinion evidence: Graat v. R. (1982), 1982 CanLII 33 (SCC), 31 C.R. (3d) 289 (S.C.C.). In addition, Paciocco and Stuesser, at pp. 187-188 in their textbook, also conclude that similar to lay opinion evidence the “ultimate issue rule” no longer applies to expert opinion evidence as a rule of general application [emphasis is mine below]: It was once said that "an opinion [whether lay or expert] can never be received when it touches the very issue before the [court]." The concern was that to allow a witness to express her "verdict" on the very issue that the trier of fact had to decide would be "usurping the functions of the jury." Put more simply, there was fear that the trier of fact might be influenced unduly by the opinion, accepting it uncritically regardless of the actual evidence in the case. The fear of undue influence is more compelling in the case of "expert" witnesses whose credentials might overwhelm the trier of fact. In Graat v. R. the accused attempted to use the ultimate issue rule to oppose the admission of lay opinions about his impairment. He argued that impairment was the very issue before the court and that to let witnesses say that his ability to drive was impaired might cause the judge simply to accept their judgment, rather than deciding the case on the evidence. Dickson J. criticized the ultimate issue rule and said that so long as the opinions were not superfluous, they were properly heard. He remarked that witnesses cannot "usurp" the role of the trier of fact because the trier is free to accept all, or part, or none of their testimony. It is the trier of fact who renders the verdict, not the witnesses. The ultimate issue rule was put to rest for lay witnesses in Graat v. R. It has since been resolved that it is also gone for expert witnesses as a rule of general application. . . . however, the fact that an expert is about to testify on one of the ultimate issues in the case will sometimes be a factor to consider in determining whether the testimony will be admitted. While the ultimate issue rule itself is gone, two of its cousins survive. The first of those rules provides that a witness cannot offer an opinion on a pure question of domestic law. The second has come to be known as the rule against oath-helping.