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10.3 Expert Opinion Evidence (General Instructions)

Note[1]

(Last revised June 2012)

[1]              You heard the evidence of (NOW), an expert witness. S/he gave an opinion about some matters that you may have to consider in deciding this case. S/he is qualified by (specify his/her training, education and experience) to give an expert opinion.

[2]              As with other witnesses, you may give the expert’s testimony as much or as little weight as you think it deserves. Just because an expert has given an opinion does not require you to accept it. You should consider the expert’s (specify: education, training and experience), the reasons given for the opinion, the suitability of the methods used and the rest of the evidence in the case when you decide how much or little to rely on the opinion.[2]

[3]              (NOW) was asked to assume certain facts. What an expert assumes or relies on as a fact for the purpose of offering his or her opinion may be the same or different from what you find as facts from the evidence introduced in this case.[3]

[4]              How much or little you rely on the expert’s opinion is up to you. But the closer the facts assumed or relied on by the expert are to the facts as you find them to be, the more helpful the expert’s opinions may be to you. To the extent the expert relies on facts that you do not find supported by the evidence, you may find the expert’s opinion less helpful.[4]

[1] Where there is a conflict in the expert opinion evidence on an essential element of the prosecutor’s case, see Final 10.4.

[2] Where the expert’s opinion is not contested and the primary facts on which it is based are not in dispute, it may be prudent to instruct the jury about the lack of any good reason to reach a contrary conclusion on the issue.

[3] If an expert witness relies on facts that are not otherwise in evidence it will likely be necessary to give the jury a limiting instruction that the expert’s statement of these facts is not evidence that those facts exist. See, R. v. Abbey, [1982] 2 S.C.R. 24; R. v. Lavallee, [1990] 1 S.C.R. 852.

[4] Where an expert relies on what the person charged said to him/her during an interview, an account that is not otherwise before the trier of fact, the limiting instruction must be carefully worded to avoid comment on the person’s failure to testify.