Onus on party adducing expert to prove underlying facts

R. v. Paszczenko, 2010 ONCA 615, released today online, is a useful source for the principle that facts underlying an expert opinion must be independently proven. Some though Abbey might be taken to the contrary but Paszczenko clarifies. Only well accepted facts within the expert's expertise may be relied on my the expert without further proof:

The Court writes:

General Considerations of Proof

[21]          There can be no dispute that the onus is on the Crown to prove the facts underlying the expert's report, including the assumptions upon which the expert relies.  As Sopinka J. noted in R. v. Lavallee, [1990] 1 S.C.R. 852, at p. 898: "before any weight can be given to an expert's opinion, the facts upon which the opinion is based must be found to exist."  See also, R. v. Grosse (1996), 29 O.R. (3d) 785 at p. 790 (C.A.), leave to appeal refused, [1996] S.C.C.A. No. 465.  As noted above, however, the issue here is not whether the Crown must prove the assumptions, but how it is required to do so.

[22]          In this respect – as the SCAJ in Paszczenko noted – the Ontario jurisprudence in the courts below falls into two categories.  The first group of authorities requires that all four of the standard assumptions on which the toxicologist opinion is based be proved by case-specific evidence: see, for example, R. v. Castro-Mendoza (November 25, 2004), Toronto (Ont. C.J.); R. v. Hansraj, [2003] O.J. No. 3746 (C.J.); R. v. Lin, 2007 ONCJ 312; R. v. Virk, [1999] O.J. No. 5524 (C.J.); R. v. Nauss, [2003] O.J. No. 5943 (C.J.); and R. v. Thompson, [2007] O.J. No. 1204 (C.J.).  The second group of authorities holds that the assumptions about elimination rates and the plateau differ from the assumptions regarding drinking before and after the incident in terms of the proof required, and that the elimination rate and plateau assumptions are matters of scientific knowledge on which the expert is entitled to rely without further proof by the Crown: see, R. v. Kim, 2007 ONCJ 488;  R. v. Lima, 2009 CanLII 49638 (Ont. S.C.); R. v. Calabretta, 2008 ONCJ 27, aff'd [2008] O.J. No. 4188 (S.C.); R. v. Rajeswaran, [2003] O.J. No. 2210 (C.J.); and R. v. Pucknell, [2000] O.J. No. 3512 (S.C.).

[23]          In my view, the latter line of jurisprudence represents the proper approach.  It is consistent with that taken by the Supreme Court of Canada in Lavallee and in S.A.B., where the distinction is made between "evidence that an expert obtains and acts upon within the scope of his or her expertise" and "evidence that an expert obtains from a party to the litigation": S.A.B., at paras. 62-63.  In the toxicology report context, this distinction has been described as the difference between "foundation facts" that must be proven in evidence (bolus drinking and post-incident drinking have been held to fall into this category), and information acted upon by an expert obtained as a result of his or her expertise (the elimination rate and plateau assumptions have been held to fall into this category).  I agree with this distinction and accept as accurate the following statement by C. Brewer J. in Kim, at para. 12:

However, it is also well established that an expert is entitled to rely on information that is widely used and acknowledged as reliable within that field and that is employed as an accepted means of making decisions within that area of expertise: see R. v. Zundel (1987), 31 C.C.C. (3d) 97 (Ont. C.A.) at 146; R. v. Lavallee, supra, per Sopinka J., concurring, at 132; R. v. Terceira (1997), 123 C.C.C. (3d) 1 (Ont. C.A.) at 37-39.  This information may form a basis for the expert's opinion without any need to lead evidence to support it.   [Emphasis added.]

[24]          In Calabretta, then Associate Chief Justice J.D. Wake came to a similar conclusion, at para. 27:

Nevertheless, accepting that there must be a basis for all four assumptions it seems that there is a difference between the first two assumptions and the latter two.  The first two assumptions, (bolus drinking) (no drinking after offence) are clearly matters of fact for the trial judge to determine on the evidence or lack thereof presented at the trial.  The latter two assumptions (rate of elimination) and (allowance for a plateau) are really matters of science upon which an expert should be able to rely.

[25]          Justice Langdon, the SCAJ in Calabretta, also accepted this analysis, at paras. 9-11.

[26]          An expert is entitled to refer to sources within his or her field to explain and support the conclusions drawn: S.A.B., at para. 63.  I conclude, therefore, that in the absence of a challenge to the expert, assumptions 3 (the elimination rate) and 4 (the plateau) need not be proved by case-specific evidence led at trial to support them, other than the expert's toxicological report filed pursuant to s. 657.3 of the Code.  Assumptions 1 (no bolus drinking) and 2 (no post-incident drinking) require case-specific proof