Legal facts shouldn’t be “alternative” ones

The “sufficient basis” requirement as an implied factor in Mohan

The Court in Mohan[1] implied — but failed to state clearly — the rule that the admissibility of expert evidence requires to show a sufficient basis for the knowledge used. This lack of proper clarification has led to inconsistency which is still present in the Canadian jurisprudence.

The trial judge in Mohan explicitly put the very basic assumption of the evidence at issue: the existence itself of any “unusual features” which would indicate “a member of a limited and distinguishable group.”[2] The judge was clear about the concern, “There is no scientific data available to warrant that conclusion. A sample of three offenders is not a sufficient basis.”[3] With no basis found, the trial judge stripped the evidence of its expert look and, as a result, rendered it inadmissible simply as a general character evidence, with nothing “expert” in its nature.[4]

Arguably, the Court of Appeal went astray, reversing the trial judge’s decision because of the logical relevance of the expert evidence.[5] Holding that the evidence “was admissible to show that the respondent was not a member of either of the unusual groups of aberrant personalities,”[6] Finlayson J.A. took the very existence of those groups for granted, relying basically on “all” of the expert’s “personal experience,”[7] however unspecific[8] it might be. The Court’s of Appeal argument, thus, missed the very gist of the problem: before deciding about the relevance of the expert knowledge, one must verify whether the knowledge exists at all. Therefore, by reversing the Court’s of Appeal decision, the Supreme Court inevitably had to have corrected this error, though, unfortunately, without stating it in an explicit way.

The Mohan criteria[9] do not include a “sufficient basis” requirement. However, one must seek this requirement somewhere within the scope of relevance and necessity first. Arguably, the “sufficient basis” requirement is hidden inside of the reliability requirement (as a part of the relevance factor). Indeed, unreliable evidence makes it legally irrelevant,[10] and thus unnecessary by definition.[11] But it seems that the Court in Mohan also placed the sufficient basis within the proper qualification criterion, which requires an expert to have “acquired special or peculiar knowledge through study or experience.”[12] This criterion presumes the existence of such knowledge (otherwise there would be nothing to acquire). Thus, arguably, to comply with this requirement, one must also first show the existence of the sufficiently reliable knowledge: “expert evidence which advances a novel scientific theory or technique is subjected to special scrutiny to determine whether it meets a basic threshold of reliability.”[13] The existence of the specific groups, suggested by the expert in Mohan, arguably amounted to a “novel” knowledge. That is what the trial judge tried to point at, saying that no scientific data existed to warrant the expert’s conclusion. Sopinka J. explicitly agreed with the trial judge: “there is no acceptable body of evidence that doctors who commit sexual assaults fall into a distinctive class with identifiable characteristics… there was no material in the record to support a finding that the profile of a pedophile or psychopath has been standardized.”[14]

This is the very point: it is impossible to credibly apply the Mohan criteria (except for the absence of an exclusionary rule) without showing first the existence of the sufficient basis for the expert knowledge. Leaving this concern outside of a court’s deliberation will lead directly to the situation where “expert evidence will be misused and will distort the fact-finding process.”[15]

The strength of the Court’s rule is undermined, however, by the word “novel,” meaning that the previously accepted (by the courts) knowledge does not require special scrutiny. But later, in Trochym[16] the Court specifically observed that “the scientific community continues to challenge and improve upon its existing base of knowledge. As a result, the admissibility of scientific evidence is not frozen in time.”[17] Unfortunately, this only extended the meaning of “novel” to some new development of the knowledge, leaving already existing controversies in some legal penumbra.

Also, Trochym improved clarity, upholding the Daubert factors[18] as a means to establish sufficient basis for the expert evidence, but later the Supreme Court added uncertainty by refusing the leave to appeal in Abbey,[19] where the use of the Daubert factors was contextually limited.[20] The Court in Abbey tried to provide alternative criteria[21] for “non-scientific” expert evidence, echoing the argument in Lavallee[22] (a pre-Mohan case) that expert’s (as, for example, physician’s) daily practice can give a “strong circumstantial guarantee of trustworthiness”[23] where his opinion is based upon evidence “of a general nature which is widely used and acknowledged as reliable by experts in that field.”[24] Strangely enough, this approach is fully consistent with the reasoning of Finlayson’s J.A.,[25] whose decision was overturned in Mohan, while arguably inconsistent with the Mohan logic and ratio on the sufficient basis issue.

Unfortunately, these uncertainties (about “old” science and non-scientific expertise) leave serious loopholes in the shield the Court in Mohan tried to build against unreliable and unnecessary expert evidence. They allow to produce to the jury a simple personal opinion based on prejudiced “common sense,” stereotypes, and insufficient knowledge — particularly under the guise of an non-scientific form of an expert opinion, and a “sound professional judgement.”[26] That is exactly what the Court fought against in Mohan. Resurfacing of the problem shows that the decision was not firm and clear enough.

[1] R v Mohan, [1994] SCJ No 36, [1994] 2 SCR 9 [Mohan]

[2] Ibid, at paras 9-11

[3] Ibid, at para 11

[4] Ibid.

[5] Ibid, at para 13, 14

[6] Ibid, at para 14

[7] Ibid, at para 12

[8] Ibid, at para 10

[9] Ibid, at para 17

[10] Ibid, at para 18

[11] Ibid, at para 22, 46

[12] Ibid, at para 27

[13] Ibid, at para 28

[14] Ibid, at para 46

[15] Ibid, at para 19

[16] R v Trochym, 2007 SCC 6, [2007] 1 SCR 239 [Trochym]

[17] Ibid, at para 31

[18] Ibid, at para 36

[19] R v Abbey, 2009 ONCA 624 (CanLII), leave to appeal to SCC refused [2010] SCCA No 125 [Abbey]

[20] Ibid, at para 114

[21] Ibid, at para 119

[22] R v Lavallee, 1990 CanLII 95 (SCC), [1990] 1 SCR 852 [Lavallee]

[23] Ibid.

[24] Ibid.

[25] Mohan, supra note 1 at para 12

[26] Abbey, supra note 19 at para 115