Executive Summary: Key Legal and Evidentiary Issues

• Whether the defendants should be granted leave under article 574 C.p.c. to file "appropriate evidence" at the pre-authorization stage of a proposed class action.
• Admissibility of an expert-style sworn declaration from Dr. William Joseph Barbaresi addressing the causes of ASD and ADHD, the plaintiffs' scientific studies, and the plaintiffs' medical records.
• Application of the criteria set out in Toledano c. Bank of Nova Scotia, requiring that pre-authorization evidence be relevant, useful, proportionate, and confined to what is strictly necessary to assess the article 575 C.p.c. criteria.
• Concern that expert opinion evidence on causation would trigger a contradictory experts' debate, which is not permitted at the authorization stage and would prompt the plaintiffs to seek a counter-expertise.
• Distinction drawn between contested scientific opinion and neutral evidence, with the SOGC's September 12, 2025 consensus statement found necessary to assess an allegation in the re-amended application.
• Timeliness of the proceeding, the initial application having been filed on October 20, 2022, with the authorization hearing set for September 10, 2026.

Facts of the case

Jade Corbeil and Merieme Hamzi are the plaintiffs in a proposed class action before the Superior Court of Quebec (Class Actions Chamber) against Johnson & Johnson and Kenvue Canada Inc. The application for authorization to institute the class action was filed on October 20, 2022; the original plaintiff, Ms. Chouinard, was substituted by Ms. Corbeil and Ms. Hamzi on April 3, 2024, following a judgment of the Court. The plaintiffs allege that regular ingestion of Tylenol — whose principal ingredient is acetaminophen — during pregnancy creates an increased risk that the unborn child will develop autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD). The proposed class covers all parents in Quebec (including any deceased parent and/or their estate) with a child whose biological mother regularly ingested Tylenol or other acetaminophen-containing products of the defendants during pregnancy, where the child then developed ASD or ADHD, and their children. On December 9, 2025, at the pre-authorization stage, the Court allowed amendments to the application and permitted a limited written examination of the plaintiffs on certain subjects, and on March 26, 2026 it maintained several objections to questions posed in that examination. By an Application for Leave to Adduce Relevant Evidence dated May 29, 2026, the defendants sought leave to file four categories of evidence: the sworn declaration of Dr. William Joseph Barbaresi, a pediatrician specialized in developmental and behavioral medicine at Boston Children's Hospital; six scientific articles published by some of the same authors as the articles filed by the plaintiffs, intended to correct or clarify them; the consensus statement of the Society of Obstetricians and Gynaecologists of Canada (SOGC) titled "SOGC Position Statement on the use of Acetaminophen for Analgesia and Fever Pregnancy" dated September 12, 2025; and extracts from the plaintiffs' medical records not produced by the plaintiffs.

Provisions and allegations at issue

This being a procedural judgment, the dispute turned on articles of the Code of Civil Procedure rather than contractual clauses. The defendants argued the evidence was necessary to complete the factual context and to allow the Court to verify whether the alleged facts appear to justify the conclusions sought (art. 575(2) C.p.c.), whether class members' claims raise identical, similar or related questions of law or fact (art. 575(1) C.p.c.), and whether the plaintiffs can be designated as representatives in light of their personal causes of action (art. 575(4) C.p.c.). The plaintiffs opposed, arguing that such evidence goes well beyond what is necessary to analyze the authorization criteria and would trigger an experts' debate that is neither desirable nor permitted at this stage, and announced that if the evidence were allowed they would be obliged to seek leave to produce a counter-expertise. Also central was paragraph 29 of the re-amended application, which alleges that, based on new research, "many doctors now recommend that women avoid or limit the taking of acetaminophen during pregnancy unless medically indicated."

The court's reasoning and analysis

Justice Eleni Yiannakis, J.C.S., applied the criteria from Toledano c. Bank of Nova Scotia: evidence at this stage is appropriate only if relevant and useful to verifying the article 575 C.p.c. criteria; it must respect the principles of reasonable conduct and proportionality (arts. 18 and 19 C.p.c.); verification of the truth of the allegations belongs to the merits, and the authorization judge must generally take the facts alleged as true unless implausible or manifestly inaccurate; and the court must not authorize evidence beyond what is strictly necessary to meet the Supreme Court's "arguable case" threshold. The Court noted these criteria do not change in a pharmaceutical file, citing Chalifoux c. Molson Coors, where only evidence raising no scientific debate or controversy was accepted, and Infineon, where the Supreme Court stressed that expert evidence is not the norm at authorization. The Court characterized the defendants' request as, in substance, permission to file an expert report in the form of a sworn declaration, while noting the plaintiffs had filed no expert report of their own. On the first point of Dr. Barbaresi's declaration — that ASD and ADHD are principally attributable to genetic risk factors — the Court held additional expert evidence was unnecessary, as the causation debate is already raised in the studies filed by the plaintiffs and the Court already has sufficient elements, having previously permitted a limited examination of the plaintiffs on family history and risk factors. On the second point — that no study demonstrates that maternal acetaminophen use actually causes ASD or ADHD — the Court found Dr. Barbaresi's interpretation of the studies would inevitably lead to an experts' debate and open the door to a counter-expertise, a situation to be avoided at all costs at authorization; the same conclusion applied to the six proposed scientific articles. The SOGC consensus statement, however, stood apart: it records that these specialists still recommend acetaminophen as first-line treatment for fever and pain during pregnancy when medically indicated, at recommended doses and for the shortest necessary duration, is in line with a Health Canada statement already in the record, and sheds light on the allegation in paragraph 29 of the re-amended application, making it necessary for the study of the authorization criteria. Finally, Dr. Barbaresi's review of the plaintiffs' medical records — noting a notable family history of ADHD and ASD for Ms. Corbeil and certain pregnancy complications for Ms. Hamzi — was found unnecessary, since the plaintiffs' answers to the written examinations are already in evidence and the expert's conclusions would only generate an experts' debate.

Ruling and outcome

Observing that the initial application was filed almost four years ago and that it is high time to proceed to the authorization debate, fixed for September 10, 2026, the Court granted the Application for Leave to Adduce Relevant Evidence in part only, authorizing solely the filing of Exhibit R-3, the SOGC consensus statement, and rejecting the remainder of the proposed evidence. The plaintiffs, Jade Corbeil and Merieme Hamzi, were therefore largely the successful parties, having defeated the admission of the expert declaration, the scientific articles, and the medical-record extracts, though the defendants obtained the limited admission of the SOGC statement. No monetary award, damages, or quantified costs were ordered; the judgment concludes with costs to follow ("frais à suivre"), so no exact amount can be determined from this decision.