Challenging the Expert Witness

13

Challenging the Expert Witness

Introduction

1.  During the last 25 years in my practice of civil and public law litigation, the role of expert witnesses has come to assume a predominant position in terms of their ability to determine the outcome of a case because of the strength of their opinion evidence.

2.  Expert witnesses are routinely retained by both parties to provide expert evidence which pertains to the subject and/or issues at hand, and to provide opinion evidence which would, but for their expertise be inadmissible. All too frequently the opinion evidence given by experts pertains to the very issues that are before the trier of fact whether it be a judge or a jury. In other words, the court hears opinions and conclusions from experts which formulates the evidence which in turn determines the outcome of the case.

3.  In my view expert witnesses provide at least two important functions which explain their importance in civil litigation today.

(a)  They provide their expert knowledge to educate the court and to explain to the court complex, scientific or technical evidence which lay people to not normally know or understand.

(b)  Secondly, expert witnesses provide opinion evidence in order to persuade the court that the inferences to be drawn from the evidence which they give, should be determinative of the issues addressed by the expert in his or her testimony.

4.  It has been my experience that given the prominence of expert evidence in today’s litigation the “fact finding” function of the judge or jury has to a significant extent been subordinated to the function of “selecting” the evidence of the most persuasive of the experts that appear before the courts.

5.  It is axiomatic that neither a judge nor a jury can know the technical and scientific information that an expert knows and understands. The Court as the finder of fact does not have the expertise to challenge the conclusion which may be made by expert witnesses when deciding which evidence to accept and which to reject. In cases of a judge alone, the problem may be compounded by the fact that the judge may be asked to rule on the admissibility of the evidence at the outset of trial.

6.  In the case of R. v. J-L.J. 2000 SCC page 51. Binnie J. states at paragraph 25 as follows:

“Expert witnesses have an essential role to play in the courts. However the dramatic growth in the frequency with which they have been called upon in recent years has led to on-going debate about suitable controls on their participation, precautions to exclude “junk science”, and the need to preserve the role of the trier of fact – the judge or the jury. The law in this regard was significantly advanced by Mohan supra, where Sopinka J. expressed such concern at paragraph 21:

Dressed up in scientific language which the jury does not easily understand, and submitted through a witness of impressive antecedents, this evidence is apt to be accepted by the jury as being virtually infallible and as having more weight than it deserves. …”

“There is also a concern inherent in the application of this criterion that experts not be permitted to usurp the functions of the trier of fact. Too liberal an approach could result in a trial’s becoming nothing more than a contest of experts, with the trier of fact acting as a referee in deciding which expert to accept.”

7.  It is my submission that the responsibility of counsel who are presenting the case becomes extremely important, because they must not only present the evidence but challenge the opposing expert through cross-examination as to his qualifications and his evidence so as to provide the trier of fact with the ability to realistically assess the evidence in question, without being overwhelmed or overly impressed with it.

8.  The role of counsel in cross-examination is to expose not only the weaknesses of the content of the expert’s report and viva voce evidence, but to challenge the witness’s ability to formulate the opinions which he holds and more importantly, to test the assumptions upon which the opinions are based.

9.  A well conducted cross-examination which both challenges the expertise of the witness, the assumptions with respect to the expert evidence which led to the opinions and the relevance of the evidence itself or its reliability may go a long way to demystifying the evidence which has been given by the expert witness, and thereby provide the judge and/or jury with the ability to consider the evidence in a more realistic and less deferential light.

10.  Conversely, unprepared counsel may exacerbate the problems faced by judges and juries attempting to comprehend scientific or expert evidence and thereby compound the confusion, by conducting an inadequately prepared cross-examination or failing to challenge the credentials of the witness or by allowing the expert to elaborate on his theories, rather than controlling the evidence and focusing upon the weaknesses of such evidence.

11.  That having been said counsel who deal with expert witnesses must acquire a great many skills, not the least of which is to comprehend what the expert understands and determine the weaknesses in that evidence.

12.  This is accomplished by having counsel’s own expert review the report of the opposing expert to provide counsel with an analysis of that report to assist in the cross-examination.

13.  Ironically what frequently occurs is that in the “battle of the experts” the expert evidence may very well neutralize itself to such an extent that it becomes difficult for the trier of fact to select between competing expert theories, such that the case will often be decided on other evidence in order to resolve the disputes. In other words both experts have provided such plausible yet dramatically opposed theories or explanations in their evidence that the trier of fact cannot select which one is preferable and is obliged to determine the case on another basis.

14.  However, what is far more likely is that the triers of fact must choose between two competing expert witnesses; therefore, it is critical for counsel to ensure that the expert opinions that are going to adopted as fact are those of his or her witness rather than those of his or her opponent.

15.  Therefore in the cross-examination of expert witnesses counsel must not only deal with the persuasive content of the opponent’s expert report together with their credentials, but persuade the court that counsel’s own expert should be preferred over that of his opponent.

16.  To that end the tactic of challenging the expert at an early stage of the proceedings and in particular at the qualification stage, in my view, is a technique which, although common place in the U.S.A., is under-utilized in Canada and Ontario.

17.  It has been my experience that at this stage in Ontario at least, there is very little resistance to the admissibility of an expert’s report or his oral expert evidence, contrary to what often occurs in cases in the U.S.A., particularly in dealing with controversial evidence in the soft sciences such as psychological and psychiatric evidence.

18.  In the United States counsel often bring pre-trial motions to challenge the relevance, authenticity and propriety of expert evidence to be adduced and at this “preliminary” stage every effort is made by counsel for the party challenging this evidence to have such evidence ruled inadmissible, and thereby avoid having to discredit the evidence once it has been received by the Court.

19.  In his article on Junk Science in the United States and the Commonwealth Yale Journal of International Law (1996) Vol. 21:(2) David Bernstein, commenting on the misuse of scientific evidence in mass toxic tort litigation (similar to the case in “A Civil Action”) stated as follows at page 124:

“An even more vociferous debate arose over the alleged misuse of scientific evidence in toxic tort litigation. Toxic tort cases involve allegations of injury from exposure to environmental pollutants or pharmaceuticals …critics began to express skepticism regarding the evidence relied upon by plaintiffs in many of these causes … plaintiffs’ attorneys often misused scientific evidence in toxic tort cases. Huber popularized the phrase “junk science” as a description of scientific evidence that is either inherently unreliable or that is being stretched well beyond its limitations.”

20.  It is my theme herein that with the proliferation of expert evidence in civil cases in Canada, the Courts should be moving towards a stricter set of rules regarding the admissibility of expert evidence; counsel, in order to anticipate this phenomenon should be far more willing to challenge an expert’s assumptions and conclusions and deal with the reliability of expert evidence at the outset, rather than allowing the evidence to stand, and then cross-examining on its content.

In this paper I will deal briefly with the following subjects.

(a)  What is expert evidence?

(b)  What are the requirements for admissibility of expert evidence in Canada?

(c)  Challenging Expert evidence as to admissibility.

(d)  How to adduce/present expert evidence.

(e)  How to attack the expert.

(f)  Conclusion.

(a) What is expert evidence?

21. In the Supreme Court of Canada case of R. v. Abbey (1982) 2 S.C.R. p. 24(3), the Court described the role of an expert witness as follows:

“With respect to matters calling for special knowledge, an expert in the field may draw inferences and state his opinion. An expert’s function is precisely this: to provide the judge and jury with a ready made inference which the judge and jury, due to the technical nature of the facts, are unable to formulate. An expert’s opinion is admissible to furnish the court with scientific information which is likely to be outside the experience and knowledge of a judge or jury. If on the proven facts a judge or jury can form their own conclusions without help, then the opinion of the expert is unnecessary.”

22.  It is asserted that expert evidence is tendered by way of an exception to the rule the evidence which generally excludes opinion evidence. The exclusion of opinion evidence is based upon the premise that it would otherwise usurp the function of the trier of fact. Therefore the existence and proliferation of expert opinion evidence has changed the landscape as to what is or is not admissible evidence such that nowadays cases are replete with transcripts of competing opinions from which the triers of fact must make a selection.

23.  In the case of R. v. A.K. and N.K. (1999) QuickLaw C. 21488 (Ontario Court of Appeal)(4) the Court dealt with opinion evidence as follows:

“The opinion rule is a general rule of exclusion. Witnesses testify as to facts. As a general rule, they are not allowed to give any opinion about those facts. Opinion evidence is generally inadmissible. Opinion evidence it generally excluded because it is a fundamental principle of our system of justice that it is up to the trier of fact to draw inferences from the evidence and to form his or her opinions on the issues in the case. Hence it is only when the trier of fact is unable to form his or her own conclusions without help, that an exception to the opinion rule may be made and expert evidence admitted. It is the expert’s precise function to provide the trier of fact with a ready made inference from the facts which the judge and jury, due to the nature of the facts, are unable to formulate.”

24.  Because expert witnesses provide the Court with the technical and scientific basis upon which to properly assess evidence, expert witnesses are permitted to testify and provide the Court with such opinion evidence.

25.  It has been suggested that one of the major functions of experts is to create new evidence in the form of opinions; this is a unique feature of expert testimony and indeed there is no other context in which a witness creates new evidence about past events and provides to the Court a set of opinions that other witnesses do not possess. See: Expert Evidence (1991) Wisconsin Law Review at page 1140.(5)

26.  Because of the ability of the expert witness to persuade the Court by providing it with inferences or opinions based upon the testimony the expert gives on complex subjects, beyond the comprehension of the triers of fact and because the impact of this evidence can be determinative, I propose to look at what the Courts have done in Canada regarding the admissibility of expert evidence.

(b) Admissibility of Expert Evidence in Canada

27. The leading Supreme Court of Canada case with respect to the determination of the criteria by which to evaluate whether expert evidence is or is not admissible is the case of R. v. Mohan (1994) 2 S.C.R. page 20(6) which states as follows:

“Admission of expert evidence depends on the application of the following criteria:

(i)  relevance;

(ii)  necessity in assisting the trier of fact;

(iii) the absence of any exclusionary rule;

(iv) a properly qualified expert.”

28. (i) Relevance - The Court elaborated on these following four criteria as follows:

“Relevance is a threshold requirement for the admission of expert evidence as with all other evidence. Relevance is a matter to be decided by a judge as a question of law. Although prima facie admissible if so related to a fact and issues that it tends to establish it, that does not end the enquiry. This merely determines the logical relevance of the evidence. Other considerations enter into the decision as to admissibility. This further enquiry may be described as a cost benefit analysis, that is whether its value is worth what it costs … evidence that is otherwise logically relevant may be excluded … if its probative value is overborne by its prejudicial effect; if it involves an inordinate amount of time which is not commensurate with its value; or if it is misleading in the sense that its effect on the trier of fact, particularly a jury, is out of proportion to its reliability.”