In White Burgess Langille Inman v. Abbott and Haliburton Co.,  2 S.C.R. 182,  S.C.J. No. 23, a decision
released shortly before the judgment under appeal, the Supreme
Court of Canada provided clarity and guidance regarding challenges to experts on the basis of bias and lack of independence.
Cromwell J., writing for the court, stated, at para. 19, that the
basic structure for the law relating to the admissibility of expert
evidence has two main components.
 The first component requires the court to consider the
four traditional “threshold requirements” for the admissibility of
the evidence established in R. v. Mohan,  2 S.C.R. 9,
 S.C.J. No. 36: ( i) relevance; ( ii) necessity in assisting the
trier of fact; ( iii) absence of an exclusionary rule; and ( iv) the
need for the expert to be properly qualified.
 The second component is a “discretionary gatekeeping
step” where “the judge balances the potential risks and benefits
of admitting the evidence in order to decide whether the potential benefits justify the risks”: para. 24. It is a cost-benefit
analysis under which the court must determine whether the
expert evidence should be admitted because its probative value
outweighs its prejudicial effect.
 The analysis under the second component is best thought
of as a specific application of the court’s general residual discretion to exclude evidence whose prejudicial effect exceeds its probative value: R. v. Bingley,  1 S.C.R. 170,  S.C.J. No.
12, 2017 SCC 12, 407 D.L.R. (4th) 383, at para. 16. As Charron
J.A. wrote in R. v. K. (A.) (1999), 45 O.R. (3d) 641,  O.J.
No. 3280 (C.A.), at para. 76, application for leave to S.C.C.
quashed  S.C.C.A. No. 16: “The balancing process which
lies at the core of the determination of the admissibility of
this kind of evidence is not unique to expert opinion evidence. It
essentially underlies all our rules of evidence.” In White Burgess,
Cromwell J. referenced Mohan and made the same point, at
paras. 19 and 20:
Mohan also underlined the important role of trial judges in assessing
whether otherwise admissible expert evidence should be excluded because
its probative value was overborne by its prejudicial effect — a residual discretion to exclude evidence based on a cost-benefit analysis: p. 21.
. . . . .
The reasons in Mohan engaged in a cost-benefit analysis with respect to
particular elements of the four threshold requirements, but they also noted
that the cost-benefit analysis could be an aspect of exercising the overall
discretion to exclude evidence whose probative value does not justify its
admission in light of its potentially prejudicial effects: p. 21.