Cinar Corporation v. Robinson 2013 SCC 73:
 For expert evidence to be admitted at trial, it must (a) be relevant; (b) be necessary to assist the trier of fact; (c) not offend any exclusionary rule; and (d) involve a properly qualified expert (R. v. Mohan,  2 S.C.R. 9). These criteria apply to trials for copyright infringement, as they do in other intellectual property cases:Masterpiece Inc. v. Alavida Lifestyles Inc., 2011 SCC 27,  2 S.C.R. 387, at para. 75.
 The Cinar appellants argue that the second criterion ― necessity of the evidence ― is not met in the case at hand. The expert evidence was not necessary to assist the court, they say, because the question of whether a substantial part has been copied must be assessed from the perspective of the lay person in the intended audience for the works at issue: see Preston v. 20th Century Fox Canada Ltd. (1990), 33 C.P.R. (3d) 242 (F.C.T.D.), aff'd (1993), 53 C.P.R. (3d) 407 (F.C.A.); Arbique v. Gabriele,  J.Q. no 3794 (QL) (Sup. Ct.), aff'd 2003 CanLII 16298 (Que. C.A.). They argue that trial judges are well placed to understand a lay person's point of view and that the assistance of an expert is unnecessary to help them grasp this perspective.
 In my view, the perspective of a lay person in the intended audience for the works at issue is a useful one. It has the merit of keeping the analysis of similarities concrete and grounded in the works themselves, rather than in esoteric theories about the works. However, the question always remains whether a substantial part of the plaintiff's work was copied. This question should be answered from the perspective of a person whose senses and knowledge allow him or her to fully assess and appreciate all relevant aspects ― patent and latent ― of the works at issue. In some cases, it may be necessary to go beyond the perspective of a lay person in the intended audience for the work, and to call upon an expert to place the trial judge in the shoes of "someone reasonably versed in the relevant art or technology": Vaver, at p. 187.