Executive Summary: Key Legal and Evidentiary Issues

• Agnico Eagle and the mis en cause sought to have the DÉCODE counter-expert report, dated 13 January 2026, dismissed before trial.
• At issue was whether the DÉCODE report improperly strayed from technical analysis into legal opinion, thereby exceeding the proper scope of expert evidence.
• Admissibility of the expert report was assessed against the four-part Mohan framework: relevance, necessity, absence of exclusionary rules, and expert qualification.
• Challenged also was whether the DÉCODE report's authors possessed the requisite technical qualifications to opine on the patented invention.
• The court noted that Agnico's own expert, Guillaume Marquis, had himself relied on a guide of legal principles provided by defence counsel, making it inconsistent to criticise the counter-report for doing the same.
• Preliminary dismissal of an expert report is an exceptional measure, warranted only where the report's probative value is so low that it is plainly outweighed by its prejudicial effect.

Facts of the case

Sylvain Plante commenced an action against Agnico Eagle – Division Laronde, alleging patent infringement in relation to Patent 255, a device he holds. The invention concerns a device that performs, in a single operation, the sequential steps of drilling, inserting resin and catalyst, and installing a rod — designed to secure a wire mesh to the ceiling of mined cavities to ensure worker safety by preventing rock or material falls. Agnico, together with mis en cause Dominic Trudel and L.J.L. Mécanique Inc., contested the claim. They argued that the patent's claims were overly broad and ambiguous, that the invention lacked novelty under section 28.2(1)(b) of the Patent Act, that it was obvious to a person skilled in the art under section 28.3, and that Plante was not the true inventor. Both sides filed expert reports. Agnico and the mis en cause retained engineer Guillaume Marquis, whose report covered patent validity, infringement allegations, and interpretation of the patent claims — all structured around a guide of legal principles prepared by defence counsel from Fasken and Cain Lamarre. Plante's side responded with a counter-expert report prepared by DÉCODE, dated 13 January 2026. Agnico and the mis en cause then brought a motion to have the DÉCODE report dismissed.

Statutory and procedural framework at issue

The motion to dismiss was grounded in article 241 of the Code of Civil Procedure (C.p.c.), which allows a party to challenge the admissibility of an expert report before trial. The admissibility criteria applied were those established by the Supreme Court of Canada in R. v. Mohan, [1994] 2 SCR 9, subsequently affirmed in White Burgess Langille Inman v. Abbott and Haliburton Co. Those criteria are: (1) relevance; (2) necessity in assisting the trier of fact; (3) absence of any exclusionary rule; and (4) sufficient qualification of the expert. The court also noted the principle of proportionality under articles 9 and 18 C.p.c., and the established rule that preliminary dismissal of an expert report is exceptional and warranted only where probative value is plainly outweighed by prejudicial effect, as affirmed in Excavations Payette ltée c. Ville de Montréal, 2022 QCCA 1393.

Court's reasoning and analysis

The court observed that Marquis's own report was explicitly structured around a guide of legal principles supplied by defence counsel, which covered matters such as claim interpretation, the definition of the person skilled in the art, prior art analysis under section 28.2, and the obviousness test under section 28.3. In that context, the court held it would be inconsistent for Agnico and the mis en cause to criticise the DÉCODE counter-report for engaging with similar legal principles, when that report was produced precisely to respond to Marquis's analysis, which had itself incorporated such considerations. On relevance, the court found that the DÉCODE report directly addressed the conclusions in the Marquis report regarding claim interpretation, the definition of the person skilled in the art, and patent validity, and thus had a direct connection to the issues in dispute. On necessity, the court held that questions concerning common general knowledge, the state of the art, and the obviousness of an invention belong to a specialised technical domain where expert evidence is in principle useful. The court further held that an expert's reference to a legal framework does not render the opinion inadmissible, provided the opinion remains grounded in a technical analysis of the relevant facts, drawing on Unigertec c. Ville de Montréal, 2022 QCCS 4151. On the question of qualifications, the court found that the criticisms raised by Agnico and the mis en cause went to the weight to be given to the DÉCODE experts' testimony, not to its admissibility, and that the curriculum vitæ of the report's signatories reflected relevant scientific knowledge, as they hold engineering qualifications with specialisations pertinent to the analysis. As for the allegation of evidence-splitting (fractionnement de la preuve), the court declined to rule on that issue at the preliminary stage, holding it should be assessed in light of all the evidence at trial. Finally, the court noted that the absence of sworn declarations from the DÉCODE experts, as required under article 235 C.p.c., was acknowledged by Plante's counsel as an oversight that would be corrected promptly.

Ruling and overall outcome

The court, presided over by the Honourable Pierre Soucy, J.C.S., dismissed the motion to reject the DÉCODE expert report in its entirety. Plante, as the party opposing the dismissal motion, was the successful party on this interlocutory application. The court ordered that the DÉCODE report dated 13 January 2026 be completed by attaching the required sworn declarations in the form prescribed by the Minister of Justice, in accordance with paragraph 3 of article 235 C.p.c., within 30 days of the judgment. Costs (frais de justice) were awarded, though no specific monetary amount was stated in the decision.