View source for Legal Requirements for Qualified Expert Evidence

{{fr|Exigences_légales_relatives_à_la_preuve_d%27expert_qualifiée}}
{{Currency2|July|2021}}
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==General Principles==
A trial judge must determine on a ''voir dire'' whether the individual is qualified as an expert, and if so, what the "nature and scope of the proposed expert evidence" will be.<ref>
{{CanLIIRP|Preeper and Doyle|ggx87|1888 CanLII 56 (SCC)| (1888), 15 SCR 401}}{{Plurality}}</ref>
The qualification process is one of delineating the boundaries of the evidence and the language used.  
<ref>
{{CanLIIRP|Abbey|259rl|2009 ONCA 624 (CanLII)|246 CCC (3d) 301}}{{perONCA-H|Doherty JA}}<br>
{{CanLIIRPC|White Burgess Langille Inman v Abbott and Haliburton Co|ghd4f|2015 SCC 23 (CanLII)|[2015] 2 SCR 182}}{{perSCC|Cromwell J}}{{atsL|ghd4f|22| to 24}}<br>
{{CanLIIRP|AK|1f9pr|1999 CanLII 3793 (ON CA)|137 CCC (3d) 225}}{{perONCA|Charron JA}} <br>
</ref> 

The judge cannot permit the expert to give an opinion on common matters or matters that the expert has no special skills, knowledge, or training. 

The qualification involves two phases. First, the adducing party "must establish the threshold requirements of admissibility" under the Mohan test.<ref>
{{supra1|White Burgess}}{{atL|ghd4f|23}}<br>
</ref>
Second, the judge must exercise discretion as a gatekeeper and balance the "potential risks and benefits of admitting the evidence."<ref>
{{ibid1|White Burgess}}{{atL|ghd4f|24}}<br>
</ref>

; Purpose
The primary purpose of the limiting of opinion evidence is to avoid usurping the trier-of-fact's authority to decision decide a case, and devolve the trial process devolving into a "trial by expert."<ref>
{{supra1|White Burgess}}{{atL|ghd4f|18}} ("The point is to preserve trial by judge and jury, not devolve to trial by expert")
</ref>

There is a danger that an improperly qualified expert will give evidence that will be misused and distort the fact-finding process.<ref>
{{CanLIIRP|Mohan|1frt1|1994 CanLII 80 (SCC)|[1994] 2 SCR 9}}{{perSCC-H|Sopinka J}} ("There is a danger that expert evidence will be misused and will distort the fact-finding process.  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.")
</ref>
This is made worse given that counsel is not an expert in the field and may not be able to critically evaluate the claims through cross-examination.<ref>
{{supra1|White Burgess}}{{atL|ghd4f|18}}  ("The risk of “attornment to the opinion of the expertˮ is also exacerbated by the fact that expert evidence is resistant to effective cross-examination by counsel who are not experts in that field")<br>
</ref>

A secondary purpose is to ensure that time and money are not wasted needlessly.<ref>
{{supra1|White Burgess}}{{atL|ghd4f|18}} ("Another well-known danger associated with the admissibility of expert evidence is that it may lead to an inordinate expenditure of time and money")<br>
{{supra1|Mohan}}{{atp|21}}<bR>
</ref>

;Court's Ongoing Obligation to Evaluate Admissibility
Courts must be "vigilant in monitoring and enforcing the proper scope of expert evidence" given the impact that they have on a trial including the risk of "usurping the role of the trier-of-fact.<ref>
{{CanLIIRP|Sekhon|g35qf|2014 SCC 15 (CanLII)|[2014] 1 SCR 272}}{{perSCC-H|Moldaver J}}{{atL|g35qf|46}}<br>
{{CanLIIRP|Shafia|gvdw4|2016 ONCA 812 (CanLII)|341 CCC (3d) 354}}{{perONCA-H|Watt JA}}{{atL|gvdw4|235}}<br>
</ref>
This supervision must occur "throughout the expert's testimony" and not simply at the ''voir dire''.<ref>
{{ibid1|Sekhon}}{{atL|g35qf|46}}<br>
</ref>

{{reflist|2}}

==Requirements to Qualify an Expert (''Mohan'' Test)==
The qualification of an expert requires a two-stage inquiry. First, the evidence must pass the four "threshold" requirements of admissibility. Second, the judge must do a cost-benefit balance the potential risks and benefits of admitting the evidence and decide whether the benefits outweigh the risks.<ref>
{{CanLIIRP|Shafia|gvdw4|2016 ONCA 812 (CanLII)|341 CCC (3d) 354}}{{perONCA-H|Watt JA}}{{AtL|gvdw4|226}}<br>
{{CanLIIRP|Abbey|259rl|2009 ONCA 624 (CanLII)|246 CCC (3d) 301}}{{perONCA-H|Doherty JA}}<br> 
{{CanLIIRPC|Parliament v Conley|jfkp5|2021 ONCA 261 (CanLII)|155 OR (3d) 161}}{{perONCA|Harvison Young JA}}{{atL|jfkp5|43}}<br>
{{CanLIIRPC|White Burgess Langille Inman v Abbott and Haliburton Co|ghd4f|2015 SCC 23 (CanLII)|[2015] 2 SCR 182}}{{perSCC|Cromwell J}} (7:0){{atsL|ghd4f|23|to 24}}
</ref>

To qualify a person as an expert, the evidence must meet the ''Mohan'' requirements:<ref>
{{CanLIIRP|Mohan|1frt1|1994 CanLII 80 (SCC)|[1994] 2 SCR 9}}{{perSCC-H|Sopinka J}} (9:0)<br>
{{CanLIIRP|J-LJ|5246|2000 SCC 51 (CanLII)|[2000] 2 SCR 600}}{{perSCC-H|Binnie J}}<br>
{{CanLIIRP|Sekhon|g35qf|2014 SCC 15 (CanLII)|[2014] 1 SCR 272}}{{perSCC-H|Moldaver J}} (5:2){{atL|g35qf|43}}<br>
</ref>
# the opinion must be ''relevant'';
# the opinion must be ''necessary'' to assist the trier-of-fact to draw the correct inference;
# the ''absence'' of any other exclusionary rule;
# the required qualifications of the proposed expert.

The Mohan test assumes that the area of science is not novel. Where the subject matter is novel, contested, or being used for a novel purpose, there is an additional requirement that the party adducing the evidence show that subject matter is reliable "for that purpose."<ref>
{{supra1|White Burgess}}{{atL|ghd4f|23}} ("At the first step, the proponent of the evidence must establish the threshold requirements of admissibility. These are the four Mohan factors ... 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: .... Relevance at this threshold stage refers to logical relevance: .. . Evidence that does not meet these threshold requirements should be excluded. Note that I would retain necessity as a threshold requirement: ...")<br>
{{supra1|JLJ}}{{ats|33, 35 to 36, 47}}<br>
{{CanLIIRP|Trochym|1qbvh|2007 SCC 6 (CanLII)|[2007] 1 SCR 239}}{{atL|1qbvh|27}}<br>
</ref>

; White/Abbey Approach to Mohan 
The preferred analytical approach to the Mohan test is to perform a two stage analysis.<ref>
{{CanLIIRP|Abbey|259rl|2009 ONCA 624 (CanLII)|246 CCC (3d) 301}}{{perONCA-H|Doherty JA}}<br> 
{{CanLIIRP|Abbey|h56zc|2017 ONCA 640 (CanLII)|350 CCC (3d) 102}}{{perONCA|Laskin JA}} (3:0){{atL|h56zc|48}}<br>
{{CanLIIRP|Farnham|gt8ss|2016 SKCA 111 (CanLII)|12 WWR 635}}{{perSKCA|Ryan-Froslie JA}} (3:0){{atL|gt8ss|81}}<br>
</ref>

; First Stage &ndash; Threshold Requirements
The first stage is to consider the "preconditions to admissibility."<ref>
{{supra1|Abbey (2009)}}{{atL|259rl|79}}<br>
{{supra1|Abbey (2017)}}{{atL|h56zc|48}}<br>
</ref>
The evidence must meet the threshold requirements of admissibility, which are:
# The opinion must be logically relevant;
# The opinion must be necessary to assist the trier of fact;
# The opinion must not be subject to any other exclusionary rule;
# The expert must be properly qualified, which includes the requirement that the expert be willing and able to fulfil the expert’s duty to the court to provide evidence that is:
## Impartial,
## Independent, and
## Unbiased.
# For opinions based on novel or contested science or science used for a novel purpose, the underlying science must be reliable for that purpose,

Should the evidence fail the requirements of the first stage, then the evidence is excluded.<ref>
{{supra1|Abbey (2017)}}{{atL|h56zc|49}} ("...if the proposed expert evidence does not meet the threshold requirements for admissibility it is excluded.")<br>
</ref> 

; Second Stage &ndash; Gatekeeper
The second stage concerns a "gatekeeper inquiry" where the judge "must identify and weigh competing considerations to decide whether, on balance, admissibility of the evidence is favoured."<ref>
{{supra1|Farnham}}{{atL|gt8ss|81}}<br>
{{supra1|White}}{{atL|ghd4f|24}} ("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”")
</ref>
This second stage is effectively a cost-benefit analysis.<ref>
{{supra1|Farnham}}{{atL|gt8ss|81}}<br>
</ref> 
Factors to consider include:<ref>
{{supra1|Abbey (2017)}}{{atL|h56zc|48}}<br>
</ref>
# Legal relevance,
# Necessity,
# Reliability, and
# impartiality, independence and absence of bias.<Ref>
{{supra1|White}} at para 54
</ref>

; Case-Specific Analysis
The analysis will be "case-specific" and will be a "function of the other evidence and issues in the case being tried."<ref>
{{supra1|Shafia}}{{AtsL|gvdw4|229|, 230 and 234}}<br>
{{CanLIIRP|D(D)|525r|2000 SCC 43 (CanLII)|[2000] 2 SCR 275}}{{perSCC-H|Major J}} (4:3){{atL|525r|12}}<br>
</ref>
Absent an error in principle or an unreasonable ruling, the judge's decision on expert evidence requires deference.<ref>
{{CanLIIRP|Natsis|hrv9x|2018 ONCA 425 (CanLII)|361 CCC (3d) 26}}{{perONCA|Pardu JA}}{{atL|hrv9x|16}} ("I begin with the observation that, absent an error in principle or an unreasonable ruling, a trial judge’s decision as to the admissibility of expert evidence is entitled to deference")<br>
{{CanLIIRP|McManus|h4c4p|2017 ONCA 188 (CanLII)|353 CCC (3d) 493}}{{perONCA|van Rensburg JA}}{{atL|h4c4p|68}}<br>
</ref>

; Impartiality
Expert evidence should be expected to be impartial to be admissible. There must not be any bias or appearance of bias.<ref>
{{CanLIIRP|Docherty|2c36p|2010 ONSC 3628 (CanLII)|[2010] OJ No 2460}}{{perONSC|Wein J}} - father of defence counsel writes psych report, found invalid<br>
</ref>

; Weight Given to Expert Evidence
Where qualification is consented to by the other counsel, it does not permit the court to assign "weight beyond what the trial judge should otherwise attribute."<ref>
{{CanLIIRx|Strickland|g20sf|2013 NLCA 65 (CanLII)}}{{perNLCA|Mercer JA}} (3:0)
</ref> 
Weight is attributed by the court based on "reasons given for the expert opinion, the evidence bearing on the basis of the expert opinion and the extent of the expert’s expertise."<ref>
{{ibid1|Strickland}}{{atL|g20sf|19}}</ref>

; Objections
Where the expert witness was not properly qualified and still gave evidence, their opinion may still be admissible absent objection from the opposing counsel.<ref>
See Opinion Evidence Outside of Qualification below</ref>

A failure of defence to make objections during trial are not likely obstacles to appeal since it is "foreseeable that defence counsel may fail to object to the testimony at the time the problematic statements are made."<ref>
{{supra1|Sekhon}}{{atL|g35qf|48}}
</ref>

; Expert Evidence Dangers
The courts "must be vigilant in monitoring and enforcing the proper scope of expert evidence" throughout the trial. Simply ruling on the Mohan criteria at the outset is not enough.<ref>
{{supra1|Sekhon}}{{atL|g35qf|46}}</ref>

Judge's must be cautious that the trial does not devolve into "trial by expert". The trier-of-fact must still be able to make "an effective and critical assessment of the evidence" that is based on "informed judgment" rather than blind faith in the expert's opinion.<ref>
{{supra1|White Burgess}}{{atL|ghd4f|18}}<br>
</ref>
To avoid this the courts as gatekeepers must watch out for:<ref>
{{supra1|White Burgess}}{{atL|ghd4f|18}}<br>
{{supra1|Shafia}}{{atL|gvdw4|233}} ("Consumption of time. Prejudice. Confusion. The danger that jurors will be unable to make an effective and critical assessment of the evidence. The complexity of the materials. The impenetrable jargon in which the opinion is clothed. Compromise of the trial process by unduly protracting and complicating proceedings:")
</ref>
* resistance to effective cross-examination by a non-expert counsel;
* potential prejudice created by the expert's reliance on unproven material not subject to cross-examination;
* the admission of "junk" science;
* the risk of distraction from a "contest of experts";
* an inordinate amount of time and money consumed by experts.
* the likelihood of confusing the trier-of-fact;
* the extent of impenetrable jargon.
* the inability of trier-of-fact from making effective and critical assessment of the evidence.

; Appellate Review
Given the "case-specific" nature of the test, the appellate court may intervene where the finding "is clearly unreasonable, contaminated by an error in principle or reflective of a material misapprehension of evidence."<ref>
{{supra1|Shafia}}{{atL|gvdw4|230}} ("The case-specific nature of the Mohan inquiry has implications for the standard of appellate review. Appellate review is not precluded, as for example, where a finding of admissibility under Mohan is clearly unreasonable, contaminated by an error in principle or reflective of a material misapprehension of evidence.")<br>
</ref>
The Court must show deferrence to the trial judge's decision.<ref>
{{supra1|Shafia}}{{atL|gvdw4|230}}<br>
</ref>

{{reflist|2}}

==Relevance==
Relevance require the judge to conduct a cost-benefit analysis to determine "whether its value is worth what is costs", which includes weighing the probative value against the prejudicial effect.<ref>
{{CanLIIRP|Sekhon|g35qf|2014 SCC 15 (CanLII)|[2014] 1 SCR 272}}{{perSCC-H|Moldaver J}}{{atL|g35qf|44}}<br>
{{CanLIIRP|Mohan|1frt1|1994 CanLII 80 (SCC)|[1994] 2 SCR 9}}{{perSCC|Cory J}}{{atps|23-24}}<br>
</ref>
 
The ''relevance'' requirement includes both ''logical relevance'' (the relationship between the evidence and the fact in issue it is being used to establish) and ''legal relevance'' (the probative value).<ref>
{{CanLIIRP|AK|1f9pr|1999 CanLII 3793 (ON CA)|137 CCC (3d) 225}}{{perONCA|Charron JA}}</ref>
In the first stage of the analysis on threshold reliability, the focus is on logical relevance.<ref>
{{CanLIIRPC|White Burgess Langille Inman v Abbott and Haliburton Co|ghd4f|2015 SCC 23 (CanLII)|[2015] 2 SCR 182}}{{perSCC|Cromwell J}}{{atL|ghd4f|23}}<br>
{{CanLIIRP|Abbey|259rl|2009 ONCA 624 (CanLII)|246 CCC (3d) 301}}{{perONCA-H|Doherty JA}}{{atL|259rl|82}}<br>
{{CanLIIRP|Shafia|gvdw4|2016 ONCA 812 (CanLII)|341 CCC (3d) 354}}{{perONCA-H|Watt JA}}{{atL|gvdw4|227}}<br>
</ref>

Logical relevance requires that the evidence "have a tendency, as a matter of human experience and logic, to make the existence or non-existence of a fact in issue more or less likely than it would be without the evidence."<ref>
{{supra1|Abbey}}{{atL|259rl|82}}<br>
{{CanLIIRP|J-LJ|5246|2000 SCC 51 (CanLII)|[2000] 2 SCR 600}}{{perSCC-H|Binnie J}} (7:0){{atL|5246|47}}<br>
{{supra1|Shafia}}{{atL|gvdw4|227}}<br>
</ref>

Expert evidence can be relevant where it establishes motive to commit the offence.<ref>
{{CanLIIRP|Ma|htv3s|1978 CanLII 2438 (ON CA)|[1978] OJ No 1425}}{{perONCA|Lacourciere JA}}<br>
{{CanLIIRP|Boucher|1f8zp|2000 CanLII 6087 (QC CA)|149 CCC (3d) 429}}{{TheCourtQCCA}} (3:0)<br>
{{CanLIIRP|Wilson and Boswell|1wcwz|2002 CanLII 49653 (ONSC)|166 CCC (3d) 294}}{{perONSC|Kruzick J}}
</ref>
It can also be relevant ot demonstrate animus towards the victim.<ref>
{{CanLIIR-N|McLeod|, [1982] OJ No 59}}<br>
{{supra1|Wilson and Boswell}}<br>
</ref>


It is not legally relevant for a qualified drug expert to say that they have never encountered a blind drug courier in their investigations.<ref>
{{supra1|Sekhon}}{{atL|g35qf|49}}
</ref>

; Anecdotal Evidence from Expert
Anecdotal evidence per se is not inadmissible through the expert, however, depending on the purpose of the expert testimony it may lack legal relevance and necessity.<ref>
{{supra1|Sekhon}}
{{CanLIIRP|Burnett|hvbfd|2018 ONCA 790 (CanLII)|367 CCC (3d) 65}}{{perONCA-H|Watt JA}} (3:0){{atL|hvbfd|58}}<br>
</ref>

{{reflist|2}}

==Necessity==
The ''necessity'' requirement is not a strict standard. It is necessary where it furnishes scientific information that is likely to be outside the experience and knowledge of the trier of fact.<ref>
{{CanLIIRP|B(RH)|1frvk|1994 CanLII 127 (SCC)|[1994] 2 SCR 656}}{{perSCC-H|McLachlin J}} (9:0)</ref>

The expert evidence must likely outside the ordinary experience and knowledge of the trier of fact.<ref>
{{CanLIIRP|Burns|1frvk|1994 CanLII 127 (SCC)|[1994] 1 SCR 656}}{{perSCC-H|McLachlin J}} (9:0){{atsL|1frvk|24| to 25}}<br>
{{CanLIIRP|Mohan|1frt1|1994 CanLII 80 (SCC)|[1994] 2 SCR 9}}{{perSCC-H|Sopinka J}} (9:0){{atps|414-415}}<br>
</ref>
The evidence should ''not'' be necessary if “on the proven facts a judge or jury can form their own conclusions without help, then the opinion of [an] expert is unnecessary”.<ref>
{{ibid1|Mohan}}{{atp|23}}<br>
{{CanLIIRP|Sekhon|g35qf|2014 SCC 15 (CanLII)|[2014] 1 SCR 272}}{{perSCC-H|Moldaver J}} (5:2){{atL|g35qf|45}}<br>
</ref>

This criterion asks whether the trier-of-fact (or "ordinary people") can form a "correct judgment about the issue" without the assistance of persons with special knowledge.<Ref> 
{{CanLIIRPC|Meady v Greyhound Canada Transportation Corp|gfvd5|2015 ONCA 6 (CanLII)|329 OAC 173}}{{perONCA|Strathy CJ}}{{AtL|gfvd5|33}} ("The application of the necessity criterion asks whether the trier is able to form a correct judgment about the issue without the assistance of persons with special knowledge.")<Br>
{{CanLIIRPC|Bonisteel|20lp2|2008 BCCA 344 (CanLII)|236 CC (3d) 170}}{{perBCCA|Levine JA}}{{atL|20lp2|68}}<Br>
{{CanLIIRP|Osmar|1qbnb|2007 ONCA 50 (CanLII)|217 CCC (3d) 174}}{{perONCA-H|Rosenberg JA}}{{atL|1qbnb|68}}
</ref>

Merely being "helpful" is not sufficient.<ref>
Mohan at p. 23 ("The word "helpful" is not quite appropriate and sets too low a standard.")
{{supra1|Greyhound}} at para 32<Br>
</ref>

However, the purpose of this element is to "ensure that the dangers associated with expert evidence are not lightly tolerated" and that mere "helpfulness" is not sufficient.<ref>
{{supra1|White Burgess}}{{atL|ghd4f|21}}<br>
</ref>

The subject-matter should be one that a lay person is "unlikely to form a correct judgment about it, if unassisted by persons with special knowledge."<ref>
{{CanLIIRPC|Kelliher (Village of) v Smith|1nmxz|1931 CanLII 1 (SCC)|[1931] SCR 672}}{{perSCC|Lamont J}} (3:2)<br>
{{CanLIIRP|DD|525r|2000 SCC 43 (CanLII)|[2000] 2 SCR 275}}{{perSCC-H|Major J}} (4:3){{atL|525r|57}}<br>
</ref>

The purpose of the necessity requirement it to protect against the dangers of expert evidence, including the risk of usurping the trier-of-fact, the consumption of time, and consumption of expenses.<ref>
{{supra1|Mohan}}{{atp|24}}<br>
{{supra1|Sekhon}}{{atL|g35qf|45}}<br>
{{supra1|DD}}<br>
</ref> 

{{reflist|2}}

==Properly Qualified Expert==
The burden is upon the party calling the witness to prove on a balance of probabilities that they are a "properly qualified expert."<ref>
{{CanLIIRP|Terceira|6gmx|1998 CanLII 2174 (ON CA)|123 CCC (3d) 1}}{{perONCA|Finlayson JA}} aff'd at 142 CCC (3d) 95, [http://canlii.ca/t/1fqmb 1999 CanLII 645] (SCC){{perSCC|Iacobucci J}}
</ref>
The determination of whether a witness is "properly qualified" is based on a "case-specific determination."<ref>
{{CanLIIRx|Vander Wier|g26vz|2013 ONSC 7390 (CanLII)}}{{perONSC|Coats J}}{{atL|g26vz|13}}<br>
</ref>
{{reflist|2}}
===Factors===
Factors to consider in the evaluation of whether the witness is "properly qualified" include:<ref>
{{CanLIIRP|Pham|g01jm|2013 ONSC 4903 (CanLII)|300 CCC (3d) 111}}{{perONSC|Durno J}}{{atL|g01jm|31}}<br>
</ref>
* The manner in which the witness acquired the special skill and knowledge upon which the application is based;
* The witness' formal education (i.e. degrees or certificates);
* The witness' professional qualifications (i.e. a member of the College of Physicians and Surgeons);
* The witness' membership and participation in professional associations related to his or her proposed evidence;
* Whether the witness has attended additional courses or seminars related to the areas of evidence in dispute;
* The witness' experience in the proposed area(s);
* Whether the witness has taught or written in the proposed area(s);
* Whether, after achieving a level of expertise, the witness has kept up with the literature in the field;
* Whether the witness has previously been qualified to give evidence in the proposed area(s), including the number of times and whether the previous evidence was contested;
* Whether the witness has not been qualified to give evidence in the proposed area(s) and if so, the reason(s) why; and
* Whether previous caselaw or legal texts have identified the contested area as a proper area for expert evidence and if so, who might give the evidence.

{{reflist|2}}
===Reliability===
A person cannot become a reliable expert by simply conducting "numerous casual conversations with drug users or traffickers". Mere anecdotal evidence cannot be tested or verified.<ref>
{{CanLIIRP|Klassen|26j|2003 MBQB 253 (CanLII)|[2003] MJ No 417}}{{perMBQB|Scurfield J}}{{atL|26j|26}} - drug expert rejected <br>
</ref>

{{Reflist|2}}

===Experience and Education===
An expert does not have to have practical experience.<ref>
e.g. {{CanLIIRP|Morgentaler (No. 2)|htxsb|1973 CanLII 1462 (QC CQ)|14 CCC (2d) 450 (Que. S.C.)}}{{perQCCQ|Hugessen J}} - gynecologist testified as expert despite having not practiced for 10 years<br>
</ref>

The essential requirement is that "he should be skilled ... that which he is called upon to give an opinion."<ref>
{{CanLIIRP|Korski|1s8h6|2007 MBQB 184 (CanLII)|218 Man R (2d) 56}}{{perMBQB|Beard J}}{{atL|1s8h6|15}} citing McWilliams' Canadian Criminal Evidence<br>
</ref>

; No Prior Qualification
There is no special rule for "first time" experts that would render them any less eligible for qualification as an expert.<ref>
{{CanLIIRx|Plourde|hn86q|2017 ABCA 367 (CanLII)}}{{perABCA|Slatter JA}} (3:0){{atL|hn86q|5}}<br>
</ref>

; Education
A formal education such as a university degree is not a necessary requirement to be an expert in an area.<ref>
{{CanLIIRP|Dugandzic|gbkv3|1981 CanLII 3117 (ON CA)|[1981] OJ No 1, 57 CCC (2d) 517}}{{perONCA|Lacourcière JA}} (3:0) - chemistry degree not required to identify a still
</ref>

However, the expertise must be gained through some form of study or experience.<ref>
{{supra1|Dugandzic}}<br>
{{CanLIIRP|Godfrey|fp05t|1974 ALTASCAD 43 (CanLII)|18 CCC (2d) 90 (Alta. S.C.A.D.)}}{{perABCA|Allen JA}} (2:1){{atps|102-104}}
</ref>
Deficiencies in expertise will usually go to weight not qualifications.<ref>
{{CanLIIRP|Marquard|1frx2|1993 CanLII 37 (SCC)|[1993] 4 SCR 223}}{{perSCC-H|McLachlin J}} (8:1){{atp|243}}<br>
</ref>

; Employment by Police Service
There is no impediment to qualification where the proposed expert is employed by police service.<ref>
{{supra1|Plourde}}{{atL|hn86q|5}}<br>
</ref>

{{Reflist|2}}

==Independence, Impartiality and Lack of Bias==
* [[Independence, Impartiality and Lack of Bias of Expert Witnesses]]

==Evaluating Novel Fields==
Novel sciences must be considered on a case-by-case basis. There are no fixed categories where the requirements for expert evidence have been met.<ref>
e.g. {{CanLIIRP|Lavallee|1fsx3|1990 CanLII 95 (SCC)|[1990] 1 SCR 852}}{{perSCC|Wilson J}} battered wife syndrome accepted as science<br>
</ref>
The courts must individually distinguish between new sciences and "junk" sciences. As such, needs "special scrutiny."<ref>
{{CanLIIRP|J-LJ|5246|2000 SCC 51 (CanLII)|[2000] 2 SCR 600}}{{perSCC-H|Binnie J}} (7:0)</ref>

There is no pre-condition that a particular field be "scientifically valid" or otherwise able to be validated by scientific methods.<ref>
{{CanLIIRP|Shafia|gvdw4|2016 ONCA 812 (CanLII)|341 CCC (3d) 354}}{{perONCA-H|Watt JA}}{{atL|gvdw4|240}}<br>
{{CanLIIRP|Abbey|259rl|2009 ONCA 624 (ONCA)|246 CCC (3d) 301, [2009] OJ No 3534}}{{perONCA-H|Doherty JA}}{{atL|259rl|109}}<br>
</ref>

Novel sciences must only be qualified if it is (1) necessary and (2) reliable<ref>
{{CanLIIRP|Terceira|6gmx|1998 CanLII 2174 (ON CA)| (1998) 123 CCC (3d) 1,}}{{perONCA|Finlayson JA}}</ref>

When evaluating scientific evidence, the Court should consider Daubert factors:<ref>
{{supra1|J-LJ}}<br>
</ref> 
#falsifiability of the theory
#peer review and publication of the theory
#known or potential rate of error and the existence of standards controlling the research on which the theory is based and
#general acceptance of the methodology underlying the theory in the scientific community.

; Unsettled Theories
The evidence can still be admissible even if the scientific theory is open to debate or that there are exceptional cases to the theory.<ref>
{{CanLIIRP|M(B)|1nptj|1998 CanLII 13326 (ON CA)|130 CCC 353 (ONCA)}}{{perONCA|Rosenberg JA}}</ref>

It is not necessary to establish that the field be one that is subject to "peer review."<ref>
{{supra1|Abbey}}{{atL|259rl|97}} - lower court erred in requiring peer review
</ref>

The fact that an area of scientific theory is open to debate and that exceptional cases fall outside the norm does not preclude the evidence from admissibility.<ref>
{{supra1|BM}} ("The fact that a scientific theory is open to debate, however, or that exceptional cases fall outside the norm, does not preclude the admissibility of opinion evidence based on that theory.")
</ref>

; Source of Expertise
Expertise "may be acquired through study."<ref>
McWilliams’ Canadian Criminal Evidence (4th) at 12:30.20.50. citing Mohan at 414</ref>

Depending on the subject, it may not be necessary that the expert has a university degree in the subject to be an expert.<ref>
{{CanLIIRP|Bulman|1qtzk|2007 ONCA 169 (CanLII)|[2007] OJ No 913 (CA)}}{{perONCA|Gillese JA}}{{atL|1qtzk|7}}</ref>

The absence of writing or publications will generally go to weight and not admissibility.<ref>
{{supra1|BM}}{{atL|1nptj|71}}<br>
</ref>

An expert is entitled to develop that expertise by observations, by talking to other experts, and by general involvement in the field.<ref>
{{CanLIIRx|Plourde|hn86q|2017 ABCA 367 (CanLII)}}{{perABCA|Slatter JA}}{{atL|hn86q|6}} - ("An expert on drug activity is entitled to develop that expertise by observations of the drug trade, by talking to other experts, and by general involvement in policing of the drug trade.")<br>
</ref>

{{Reflist|2}}

==Cost/Benefit Analysis==
The secondary stage of analysis is the gatekeeping function of the court to exclude certain types of expert evidence.

The role as "gatekeeper" does not end once the judge determines that the expert is permitted to testify based on their qualifications and the content of their report.<Ref>
{{CanLIIRPC|Bruff-Murphy v Gunawardena|h4c7f|2017 ONCA 502 (CanLII)|414 DLR (4th) 65}}{{perONCA|Hourigan JA}}{{atsL|h4c7f|62| to 66}}, leave to appeal refused, [2017] S.C.C.A. No. 343<br>
{{CanLIIRP|Sekhon|g35qf|2014 SCC 15 (CanLII)|[2014] 1 SCR 272}}{{perSCC-H|Moldaver J}}{{atsL|g35qf|46| to 47}}<Br>
{{CanLIIRPC|Parliament v Conley|jfkp5|2021 ONCA 261 (CanLII)|155 OR (3d) 161}}{{perONCA|Harvison Young JA}}{{atL|jfkp5|45}}
</ref>
The judge must maintain a "cautious delineation of the scope of the... evidence and strict adherence to those boundaries, if the evidence is admitted."<Ref>
{{ibid1|Parliament}} at paras 45 to 47
</ref>
The residual discretion to exclude evidence where the prejudicial effect outweighs the probative value continues throughout the testimony.<ref>
{{ibid1|Parliament}} at para 48<Br>
{{CanLIIRP|White|fkg70|2011 SCC 13 (CanLII)|[2011] 1 SCR 433}}{{perSCC|Rothstein J}}{{atL|fkg70|50}}<Br>
{{CanLIIRP|Bingley|gxn04|2017 SCC 12 (CanLII)|[2017] 1 SCR 170}}{{perSCC-H|McLachlin CJ}}{{atL|gxn04|30}}<Br>
</ref>

; Discretionary Exclusion of Qualified Expert Evidence
Qualified expert evidence can nonetheless be excluded if:<ref>
{{ibid1|DD}}</ref>
# the evidence would tend to usurp the duty of the trier of fact
# the prejudicial effect outweighs the probative value
# the time required outweighs its probative value
# the cost required outweighs the probative value
# the influence of the evidence outweighs the evidence's reliability.

The proposed expert must have some indicia of scientific knowledge. It cannot be admitted if the witness is giving personal opinions based on their experience or knowledge from "some" literature and interviews.<ref>
{{CanLIIRP|Bedford|1fb3f|2000 CanLII 2487 (ON CA)|143 CCC (3d) 311}}{{perONCA|Finlayson JA}} (3:0)</ref>

==Other Qualification Issues==
A final draft going to peer review is relevant evidence for disclosure.<Ref>
{{CanLIIRP|Natsis|hrv9x|2018 ONCA 425 (CanLII)|361 CCC (3d) 26}}{{perONCA|Pardu JA}}{{atsL|hrv9x|25| to 34}}
</ref>

===Defence Obligation to Disclose===
Given the different disclosure obligations between Crown and defence. There may be times where the Crown would need to disclose drafts of the expert reports while defence would not.<ref>
{{CanLIIRx|CG|hvkrv|2018 ONSC 6204 (CanLII)}}{{perONSC|Bell J}}
</ref>

The defence however are required to disclose anything that the exported used to form the basis of their opinion.<ref>
{{ibid1|CG}}{{atL|hvkrv|16}} ("... Although the issue in Friskie was the extent to which the Crown was entitled to disclosure of materials provided to a defence expert, it is clear that what the Crown was seeking and what the court ultimately ordered to be disclosed were materials that formed the foundation of the expert’s report.  Once an expert witness takes the stand, that witness can no longer be characterized as offering private advice to a party; rather, they are offering an opinion for the assistance of the court and the opposing party must be given access to the foundation of such opinions to test them adequately ..."}}<br>
{{CanLIIRP|Friskie|1c7ws|2001 CanLII 392 (SK PC)|49 WCB (2d) 375}}{{perSKPC|Snell J}}<br>
{{CanLIIRP|Stone|1fqn2|1999 CanLII 688 (SCC)|[1999] 2 SCR 290}}{{perSCC-H|Bastarache J}}{{atL|1fqn2|99}}<br>
</ref>

{{reflist|2}}