White Burgess Langille Inman v. Abbott and Haliburton Co., 2015 SCC 23 released this week largely rewrites the law on admissibility of expert evidence.
The Mohan test is replaced by a two stage test, as from Abbey, and an independence requirement is inserted as a condition precedent to admission:
 At the first step, the proponent of the evidence must establish the threshold requirements of admissibility. These are the four Mohan factors (relevance, necessity, absence of an exclusionary rule and a properly qualified expert) and in addition, in the case of an opinion based on novel or contested science or science used for a novel purpose, the reliability of the underlying science for that purpose: J.-L.J., at paras. 33, 35-36 and 47; Trochym, at para. 27; Lederman, Bryant and Fuerst, at pp. 788-89 and 800-801. Relevance at this threshold stage refers to logical relevance: Abbey (ONCA), at para. 82; J.-L.J., at para. 47. Evidence that does not meet these threshold requirements should be excluded. Note that I would retain necessity as a threshold requirement: D.D., at para. 57; see D. M. Paciocco and L. Stuesser, The Law of Evidence (7th ed. 2015), at pp. 209-10; R. v. Boswell, 2011 ONCA 283, 85 C.R. (6th) 290, at para. 13; R. v. C. (M.), 2014 ONCA 611, 13 C.R. (7th) 396, at para. 72.
 At the second discretionary gatekeeping step, the judge balances the potential risks and benefits of admitting the evidence in order to decide whether the potential benefits justify the risks. The required balancing exercise has been described in various ways. In Mohan, Sopinka J. spoke of the "reliability versus effect factor" (p. 21), while in J.-L.J., Binnie J. spoke about "relevance, reliability and necessity" being "measured against the counterweights of consumption of time, prejudice and confusion": para 47. Doherty J.A. summed it up well in Abbey, stating that the "trial judge must decide whether expert evidence that meets the preconditions to admissibility is sufficiently beneficial to the trial process to warrant its admission despite the potential harm to the trial process that may flow from the admission of the expert evidence": para. 76.
 In my opinion, concerns related to the expert's duty to the court and his or her willingness and capacity to comply with it are best addressed initially in the "qualified expert" element of the Mohan framework: S. C. Hill, D. M. Tanovich and L. P. Strezos, McWilliams' Canadian Criminal Evidence (5th ed. (loose-leaf)), vol. 2, at s. 12:30.20.50; see also Deemar v. College of Veterinarians of Ontario, 2008 ONCA 600, 92 O.R. (3d) 97, at para. 21; Lederman, Bryant and Fuerst, at pp. 826-27; Halsbury's Laws of Canada: Evidence, at para. HEV-152 "Partiality"; The Canadian Encyclopedic Digest (Ont. 4th ed. (loose-leaf)), vol. 24, Title 62 ― Evidence, at §469. A proposed expert witness who is unable or unwilling to fulfill this duty to the court is not properly qualified to perform the role of an expert. Situating this concern in the "properly qualified expert" ensures that the courts will focus expressly on the important risks associated with biased experts: Hill, Tanovich and Strezos, at s. 12:30.20.50; Paciocco, "Jukebox", at p. 595.