Expert witnesses need not be independent, Supreme Court rules

Expert witnesses who are not independent can nonetheless provide independent testimony — so ruled the Supreme Court of Canada today in White Burgess Langille Inman v. Abbott and Haliburton, a finely crafted decision that clarifies the test for admissibility of expert testimony.

Abbott and Haliburton was one of 38 respondents, all hardware stores in Nova Scotia that had joined forced to create a buyer’s group with greater negotiating power. The appellant, WBLI, had been the group’s accounting firm.

Unsatisfied with WBLI’s work, the hardware group moved their auditing to Grant Thornton’s office in Kentville, N.S. The group then launched an action against WBLI for professional negligence, wherein they relied upon expert testimony from Susan MacMillan, an auditor in Grant Thornton’s Halifax office.

WBLI objected, arguing that MacMillan’s testimony could not be independent given her relationship to the firm, which now worked the hardware group. WBLI brought a motion for summary dismissal.

The motions judge agreed with WBLI, but was overturned on appeal. Today’s decision, written by Justice Thomas Cromwell on behalf of a unanimous court, upholds the appeal court ruling.

Cromwell begins by underscoring the importance of independent expert testimony: “The question on this appeal is whether one of these basic standards for admissibility should relate to the proposed expert’s independence and impartiality. In my view, it should.”

That being said, Cromwell goes on to explain that the basic threshold for admissibility does not hinge on whether the expert is in a conflict of interest — but rather, whether the conflict precludes the possibility of independent testimony.

“When looking at an expert’s interest or relationship with a party, the question is not whether a reasonable observer would think that the expert is not independent,” the decision states. “The question is whether the relationship or interest results in the expert being unable or unwilling to carry out his or her primary duty to the court to provide fair, non-partisan and objective assistance.”

A trial judge may later conclude that the expert testimony is so conflicted that it must be expunged, but it’s not a threshold criterion, and it’s not up to a motions judge to make that call.

As the decision states, “A motions judge . . . should generally not engage in the second step cost-benefit analysis. That cost-benefit analysis, in anything other than the most obvious cases of inadmissibility, inevitably involves assigning weight — or at least potential weight — to the evidence.”

Brian Murphy, who represented the hardware group before the courts, calls the decision “the definitive ruling on independence of expert evidence for admissibility in trial cases in Canada.”

“Whether you’re biased or independent or fraudulent or unqualified or a junk expert witness, whatever — the issue is whether that should be dealt with at the gatekeeper stage on admissibility, or whether it should be let in and weighed by a judge.”

Today’s decision, Murphy says, reiterates the test for admissibility laid out in 1994 in R. v. Mohan, which establishes a two-step process. The first, to be decided by a motions judge, determines whether the testimony has: (1) relevance, (2) necessity, (3) absence of an exclusionary rule, and (4) a properly qualified witness.

The second step requires the trial judge to conduct a cost-benefit analysis in order to determine whether the testimony is beneficial to the trial process overall.

The question of independence, however, was never fully answered in Mohan, says Murphy.

“I’ve gone to a number of legal seminars on expert evidence and listened to the audience. And a number of them would get up and say, ‘Can you believe that the Nova Scotia Court of Appeal is saying that you don’t have to be independent? And can you believe that that the Supreme Court of Canada is going to have to answer this question?’”

Believe it or not, the highest court in the land has indeed pronounced on the issue: independent testimony is not the exclusive domain of independent witnesses.

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