# Expert Evidence — Admission Protocol Systematic checklist for admitting or challenging expert evidence in Canadian civil proceedings. --- ## Threshold: The Mohan Test Before an expert may give opinion evidence, the party proposing must establish (*R v Mohan* 1994 SCC): ``` □ 1. RELEVANCE The proposed opinion is logically probative of a fact in issue □ 2. NECESSITY IN ASSISTING THE TRIER OF FACT The subject matter is outside the ordinary experience and knowledge of the trier of fact Not just helpful — genuinely necessary □ 3. ABSENCE OF ANY EXCLUSIONARY RULE No hearsay problem, no ultimate-issue problem, no other rule bars admission □ 4. PROPERLY QUALIFIED EXPERT Special or peculiar knowledge through study or experience Qualifications must match the specific opinion offered ``` --- ## The Gatekeeping Function (post-White Burgess) Even where Mohan is satisfied, the trial judge exercises a residual gatekeeping discretion: ``` □ 1. COST-BENEFIT ANALYSIS Probative value vs prejudicial effect Including risk of the expert usurping the trier's function □ 2. RELIABILITY OF METHODOLOGY Is the underlying discipline reliable? Are the specific methods used generally accepted? Peer review, testing, error rates (Daubert-type factors, though Canada has not formally adopted Daubert) □ 3. INDEPENDENCE AND IMPARTIALITY The expert must be independent of the parties Must be capable of giving a fair, objective, non-partisan opinion Bias or lack of independence can be fatal to admission (White Burgess Langille Inman v Abbott 2015 SCC) ``` --- ## The Expert's Duty to the Court Recognized expert obligations: - **Independence** — from the parties and their positions - **Impartiality** — fair consideration of all evidence - **Non-advocacy** — not to argue for the party who retained them - **Disclosure** — of methods, sources, assumptions, limitations - **Consideration of alternatives** — acknowledgment of contrary views In BC Supreme Court, experts are required to sign a certificate acknowledging these duties (verify current Rule text). --- ## The Written Report ### Required Contents Most jurisdictions require expert reports to disclose: - Expert's qualifications - The issue on which the opinion is sought - The methods used - The sources of information relied on - The reasoning connecting sources to opinion - The specific opinions - Any assumptions - Any limitations or qualifications - Any dissenting views in the field the expert considered ### Timing Reports must be delivered in advance of trial or hearing according to the applicable rules. Late-delivered reports may be excluded. ### The Rebuttal / Responding Report An opposing expert may file a report responding to the first expert's report. Rules govern timing and scope. --- ## Common Challenges to Expert Evidence ### Qualifications Challenge: the expert is not qualified in the specific area of opinion. - Requires close attention to what the expert is being called to opine on vs what their qualifications actually cover - General experience in a field ≠ expertise in every sub-area ### Independence Challenge: the expert is aligned with the party rather than independent. - Financial relationships beyond fee for the report - Prior advocacy positions on the same issue - Personal relationships with counsel or parties - Frequency of appearance for one side ### Methodology Challenge: the methodology used is not reliable. - Not generally accepted in the discipline - Not applicable to the specific circumstances - Applied incorrectly - Based on insufficient data ### Factual Foundation Challenge: the expert's opinion rests on facts not established in evidence. - Expert opinions cannot fill factual gaps - Assumptions must be reasonable and be tested - Facts assumed must be proved through admissible evidence ### Ultimate Issue Challenge: the opinion resolves the ultimate legal question rather than providing information for the trier to decide. - Modern approach permits some ultimate-issue opinions but with caution - Legal conclusions remain for the court ### Scope of Cross-Examination - Qualifications - Bias and independence - Assumptions - Alternative methodologies - Facts contradicting the assumptions - Prior inconsistent positions --- ## The Voir Dire (When Contested) If the qualification of the expert is contested, a voir dire may be conducted: 1. Expert testifies to qualifications 2. Cross-examination on qualifications 3. Argument on Mohan criteria 4. Court rules on qualification 5. If qualified, expert then gives evidence in chief In administrative proceedings, this may be handled more informally, sometimes as an admissibility objection during the hearing. --- ## Challenging Opposing Expert Reports — Pre-Hearing Steps Before the hearing: ``` □ Read the report multiple times using critical-reading protocols □ Verify the expert's qualifications independently □ Identify all assumptions □ Verify each assumption against admissible evidence □ Check citations — do they say what the report claims? □ Consider retaining a rebuttal expert □ Consider requesting the expert's file / working papers □ Prepare cross-examination outline ``` --- ## Retaining Your Own Expert — Checklist ``` □ SCOPE Clearly define what the expert is being asked to opine on Do NOT retain to advocate for a predetermined conclusion □ QUALIFICATIONS Confirm expertise matches the required opinion area Check for prior expert testimony (creates public record) Check for any conflicts of interest □ INDEPENDENCE Ensure the retainer preserves independence No contingency on the outcome Reasonable fee for time, not for result □ INSTRUCTIONS Provide all relevant facts, including those unfavourable Provide access to underlying data Do NOT script the opinion □ DRAFT REVIEW Review draft for compliance with disclosure requirements Do not attempt to change the substantive opinion Verify all assumptions are documented □ FINAL REPORT Independent execution by the expert Full compliance with rules Prepared for delivery within timeline ``` --- ## When Expert Evidence Fails Common reasons expert evidence gets excluded or given little weight: - **Advocacy** — expert took sides instead of giving objective opinion - **Scope creep** — opinions outside the retained scope - **Unstated assumptions** — assumptions the expert didn't disclose - **Contested methodology** — methods not generally accepted - **Insufficient qualifications** — expertise misalignment - **Prior inconsistent positions** — expert said the opposite before - **Poor report drafting** — reasoning gaps, missing sources - **Poor cross-examination performance** — expert unable to defend positions