Expert evidence in the context of novel science

R. v. Aitken, 2012 BCCA 134 considers the admission of what appears to be novel science as part of expert evidence.  The specific question was whether a podiatrist could evidence about an individual’s gait.  In considering the question the Court gives a useful review of the admissibility of expert evidence in the context of novel science:

 

 

[70]         In Mohan at p. 20, Sopinka J. identified the following criteria for the admissibility of expert opinion evidence:

 

1)  Relevance;

 

2)  Necessity in assisting the trier of fact;

 

3)  The absence of any exclusionary rule; and

 

4)  A properly qualified expert.

 

[71]         In R. v. Abbey, 2009 ONCA 624, 97 O.R. (3d) 330, Doherty J.A. suggested a two-step process for the assessment of expert evidence that was intended to “facilitate the admissibility analysis and the application of the Mohan criteria” (para. 77).  This approach, applied in British Columbia in Reference re: Section 293 of the Criminal Code of Canada, 2011 BCSC 1588 starting at para. 73, and referred to in United City Properties Ltd. v. Tong, 2010 BCSC 111 at para. 66, does not alter the substance of the analysis under Mohan.  Rather, Doherty J.A.’s approach highlights the cost-benefit analysis that is essential to the application of the Mohan test (see p. 20) but perhaps not obvious from the enumerated criteria.

 

[72]         Under the first step of the inquiry as structured in Abbey, the trial judge must conduct a “rules-based” analysis to assess compliance with certain “preconditions to admissibility”.  These preconditions are set out at para. 80:

 

·        the proposed opinion must relate to a subject matter that is properly the subject of expert opinion evidence;

 

·        the witness must be qualified to give the opinion;

 

·        the proposed opinion must not run afoul of any exclusionary rule apart entirely from the expert opinion rule; and

 

·        the proposed opinion must be logically relevant to a material issue.

 

[73]         Of the identified preconditions, it is primarily the requirement for a properly qualified expert that is in issue on this appeal.  In her treatment of this criterion, the trial judge identified the proper test, which is set out at p. 25 of Mohan: “the evidence must be given by a witness who is shown to have acquired special or peculiar knowledge through study or experience in respect of the matters on which he or she undertakes to testify”.

…

 

[76]         The second step of the analysis as structured in Abbey consists of what Doherty J.A. termed “the ‘gatekeeper’ phase of the admissibility inquiry” (para. 78).  In this phase, the trial judge must exercise judicial discretion to determine whether the benefits associated with the evidence outweigh the costs.  This determination involves consideration of necessity (para. 93), which is not the central issue here, but which requires that the expert opinion convey information “which is likely to be outside the experience and knowledge of a judge or jury” (Mohan at p. 23, citing R. v. Abbey, [1982] 2 S.C.R. 24).

 

[77]         The cost-benefit analysis also requires consideration of the legal relevance of the proposed evidence, meaning that its probative value must outweigh its prejudicial effect (Mohan at p. 20).  As stated by Doherty J.A., “Evidence that is relevant in the sense that it is logically relevant to a fact in issue survives to the ‘gatekeeper’ phase where the probative value can be assessed as part of a holistic consideration of the costs and benefits associated with admitting the evidence” (Abbey, para. 84).

 

[78]         Consideration of the probative value of expert opinion evidence requires consideration of its reliability:

 

When one looks to potential probative value, one must consider the reliability of the evidence. Reliability concerns reach not only the subject matter of the evidence, but also the methodology used by the proposed expert in arriving at his or her opinion, the expert’s expertise, and the extent to which the expert is shown to be impartial and objective (Abbey, para. 87).

 

[79]         Where the proposed opinion is scientific in nature, the Daubert factors, outlined above, may be applicable.  However, Abbey, which concerned the evidence of a sociologist who was an expert in urban street gang culture in Canada, makes it clear that the Daubert factors are not essential to the reliability inquiry where the proffered evidence is based on specialized knowledge acquired through training or experience in a particular discipline:

 

Scientific validity is not a condition precedent to the admissibility of expert opinion evidence. Most expert evidence routinely heard and acted upon in the courts cannot be scientifically validated. For example, psychiatrists testify to the existence of various mental states, doctors testify as to the cause of an injury or death, accident reconstructionists testify to the location or cause of an accident, economists or rehabilitation specialists testify to future employment prospects and future care costs, fire marshals testify about the cause of a fire, professionals from a wide variety of fields testify as to the operative standard of care in their profession or the cause of a particular event. Like Dr. Totten, these experts do not support their opinions by reference to error rates, random samplings or the replication of test results. Rather, they refer to specialized knowledge gained through experience and specialized training in the relevant field. To test the reliability of the opinion of these experts and Dr. Totten using reliability factors referable to scientific validity is to attempt to place the proverbial square peg into the round hole (Abbey, para. 109).

 

[80]         In my view, the forensic gait analysis provided by Mr. Kelly in the present case falls into the category of expert opinion evidence based on “specialized knowledge gained through experience and specialized training”.  In determining the admissibility of Mr. Kelly’s evidence, the trial judge did not err in failing to consider indicia of scientific validity such as peer review, rate of error and adherence to a scientific method.  These factors have limited relevance in a case like the one at hand where a witness’s expertise is gained over a period of years through observation and experience in the professional realm.

 

[81]         Abbey indicates that the scope of expert evidence must be appropriately limited to make sure that the proposed opinion does not go directly to the ultimate issue in the case and thus present the jury with a ready-made inference of guilt (paras. 65 and 70).  Constraining expert opinion evidence in this fashion responds to the concern identified in Mohan that “experts not be permitted to usurp the functions of the trier of fact” (p. 24).  As stated by Major J. in R. v. D.D., 2000 SCC 43, [2000] 2 S.C.R. 275, “Faced with an expert’s impressive credentials and mastery of scientific jargon, jurors are more likely to abdicate their role as fact-finders and simply attorn to the opinion of the expert in their desire to reach a just result” (para. 53).

 

[82]         Applying this approach, Doherty J.A. stated in Abbey that it was inappropriate for the expert sociologist in that case to testify that the tear drop tattoo on the face of the accused was related to the murder of a rival gang member.  However, he found it was appropriate for the expert to provide evidence as to the possible meanings of a tear drop tattoo on the face of a young male member of an urban street gang, namely that a fellow gang member or family member had died, that the wearer of the tattoo had served a term in jail, or that the wearer of the tattoo had murdered a rival gang member.

 

…

[85]         I consider these comments of Doherty J.A. in Abbey to be apposite in the present case:

 

... I doubt that the jury would have difficulty critically evaluating [the expert’s] opinion. There was nothing complex or obscure about his methodology, the material he relied on in forming his opinion or the language in which he framed and explained his opinion. As when measuring the benefits flowing from the admission of expert evidence, the trial judge as “gatekeeper” must go beyond truisms about the risks inherent in expert evidence and come to grips with those risks as they apply to the particular circumstances of the individual case (para. 92).

 

[86]         Writing for the majority in D.D., Major J. observed that a deficiency sometimes found in expert opinions is that they may be based on unsworn material in the form of academic literature and out-of-court interviews.  This particular objection is not engaged on the facts of the present case as Mr. Kelly formulated his opinion based on real and demonstrative video evidence that was admitted at trial before the jury and provided to the jury members for their own inspection and consideration.  The evidence of the expert was before them to provide assistance in their evaluation of the images, so that they might utilize the knowledge acquired by Mr. Kelly through his training and experience in arriving at their own conclusions regarding the identity of the shooter.

 

The English Cases

 

[87]         The case law from England is, in my opinion, supportive of the admission of forensic gait analysis, which has been admitted there to assist with identification.  The respondent referred the Court to the decisions of R. v. Dean, [2004] EWCA Crim 319, R. v. Ciantar, [2005] EWCA Crim 3559, and R. v. Otway, [2011] EWCA Crim 3.  Having regard to what seems to be a pattern of increasing duration for trials, the expansion of the parameters of expert evidence is not something necessarily to be viewed with unalloyed enthusiasm.  However, domestic courts do have to take account of developments in the law in other Commonwealth jurisdictions, and this type of evidence appears to be increasingly accepted in proceedings in England.

 

[88]         The appellant challenges the applicability of the English cases on the basis that the Mohan test differs in significant ways from the test governing the admissibility of expert evidence in the U.K., which the appellant describes as requiring only relevance and a properly qualified expert.  It is asserted that this test lacks consideration of the potential cost of expert evidence, which is an essential part of the “made-in Canada solution” of the Mohan test for admissibility.

 

[89]         Of the three decisions referred to by the respondent, Otway, which was released after the trial judge’s decision in the present matter, contains the most fulsome discussion of forensic gait analysis measured against the criteria for the admission of expert evidence.  These criteria are set out in R. v. Luttrell, [2004] EWCA Crim 1344 at paras. 32-34, cited in Otway at para. 17.

 

[90]         In addition to requiring logical relevance and a properly qualified expert, it is requisite “that study or experience will give a witness’s opinion an authority which the opinion of one not so qualified will lack”.  This condition is made up of two parts.  First, it must be determined “whether the subject matter of the opinion is such that a person without instruction or experience in the area of knowledge or human experience would be able to form a sound judgment on the matter without the assistance of witnesses possessing special knowledge or experience in the area” (Luttrell, para. 32).  This particular requirement is clearly of the same nature as the requirement for necessity under the Mohan test.

 

[91]         Then it must also be determined “whether the subject matter of the opinion forms part of a body of knowledge or experience which is sufficiently organised or recognised to be accepted as a reliable body of knowledge or experience” (Luttrell, para. 32).  This requirement, in my view, speaks to the need for an assessment of reliability.  At para. 34, the Court in Luttrell rejected the use of scientific indicia of reliability as a general requirement for admissibility: “But a skill or expertise can be recognised and respected, and thus satisfy the conditions for admissible expert evidence, although the discipline is not susceptible to this sort of scientific discipline.”  This statement appears to be in accord with the analysis set forth in Abbey by Doherty J.A.

 

[92]         Consistent with the requirements under the Mohan test, the decision in Otway took account of the potential cost of expert evidence, and specifically the danger that the trier of fact would be overly influenced by the expert’s opinion.  Having ruled that, in the case of a podiatrist, “it is a necessary condition of admissibility that the witness is able to demonstrate to the court the features of comparison upon which his opinion is formed” (para. 22), the Court held:

 

... We entertain no doubt that the jury was in a position to follow and assess the value of [the podiatrist’s] evidence. There is no danger here that the jury was being invited simply to take Mr Blake’s comparison on trust. We agree with Maddison J, however, that Mr Blake’s ability safely to express his ultimate conclusion in terms of probability of a match, even probability based on Mr Blake’s clinical experience, was insufficiently established. It is important that juries are not misled to an over-valuation of comparison evidence (para. 22).

 

As in the present case, the expert podiatrist in Otway was not permitted to provide the jury with an estimate of the statistical prevalence of the observed gait characteristics.  I consider that it was prudent for the trial judge to so limit the parameters of permitted evidence in the case at bar.

 

[93]         The criteria for admissibility of expert evidence in the U.K. as outlined and applied in Otway require logical relevance, a properly qualified witness and necessity and reliability.  As well, there should be a consideration of the dangers associated with expert evidence in terms of its impact on the trier of fact.  These criteria are very similar to the analysis applicable in Canada under Mohan.

 

[94]         As observed in Otway, each application to adduce expert evidence must be individually assessed in any given case.  However, there is a high level of factual similarity between Otway and the present matter, that, in my opinion, makes the reasoning in Otway of assistance here.  Based on his review of video footage, the podiatrist in Otway was “permitted to give evidence in which he identified the similarities between the walking gait of the appellant and the walking gait of the suspect” (para. 12).  The trial judge permitted the same type of opinion evidence to be adduced before the jury in the instant case.

 

[95]         The appellant in Otway challenged the admissibility of the podiatrist’s evidence on grounds very similar to those raised by counsel in the case at bar.  It was asserted that the podiatrist’s evidence had not been “tested in field conditions, subjected to peer review and publication, tested for a potential or known rate of error or subjected to verifiable standards” (para. 18).  These assertions appear to have been dealt with by reference to the decision in Luttrell, which, as noted above, establishes that recognized skill or expertise in a non-scientific discipline can satisfy the conditions for the admissibility of expert evidence.  The Court further held that, based on precedent, the admissibility of the podiatrist’s evidence was not dependent upon the existence of a database capable of generating statistical probabilities, and that it was sufficient that his evidence was “the consequence of personal experience” (para. 19).