The Divisional Court’s decision in Donna Pelrine, by her Estate Trustee James Pelrine et al. v. Chung et al.[1], released on July 30, 2026, provides important guidance on the proper interpretation and application of Rule 53.08 of the Rules of Civil Procedure in the context of late served expert reports.

In March 2022, Rule 53.08 was amended.[2] The amended Rule provides that, where evidence is admissible only with leave of the trial judge because of a failure to comply with an applicable deadline, leave may be granted where the party responsible for the failure satisfies the Court that there is a reasonable explanation for the failure and that granting leave would not cause non-compensable prejudice to the opposing party or undue delay in the conduct of the trial.

Following the amendment, a large body of Superior Court jurisprudence treated this amended Rule as imposing a conjunctive test. On that interpretation, both requirements had to be independently satisfied. If the moving party failed to establish a reasonable explanation for the delay, the analysis likely effectively ended, even where the late evidence caused no prejudice and had no impact on the scheduled trial date.

The Divisional Court in Pelrine rejected such a rigid approach.

The case arose from a medical malpractice action in which the defendant sought leave to rely upon late served expert reports. The explanations advanced for the delay largely reflected inadvertence and mistakes on the part of counsel in arranging for and serving the reports, rather than circumstances beyond the defendant’s control.

The motion judge concluded that the defendant had failed to establish a reasonable explanation and therefore refused leave.[3] Importantly, however, the motion judge expressly recognized the severity and “harshness” of the result in his decision.[4] The reports had been served more than a year before the scheduled trial, there was little risk of an adjournment, and the plaintiffs had sufficient time to respond. The motion judge nevertheless considered himself constrained by what he regarded as the conjunctive nature of Rule 53.08. In his view, the absence of a reasonable explanation was determinative regardless of the absence of prejudice or trial delay.

The motion judge further reasoned that this result reflected a deliberate policy choice underlying the 2022 amendment. There was discussion about how the prior version of Rule 53.08 had operated too readily as an “escape clause” from expert report deadlines and had contributed to broader delay within the civil justice system.[5] The stricter wording of the amended Rule was therefore intended to ensure that failures to comply with procedural deadlines had meaningful consequences, even where those consequences were ultimately as a result of “sins of counsel.”

The Divisional Court disagreed with that interpretation. Justice Firestone held that the motion judge had misdirected himself by treating the reasonable explanation requirement as an isolated threshold issue and by failing to give adequate consideration to the broader interests of justice.[6] Although the Divisional Court accepted that Rule 53.08 contains both a reasonable explanation requirement and a prejudice and delay requirement, it held that those considerations are not to be applied in isolation from one another.

Rather, the Court held that Rule 53.08 must be interpreted and applied in conjunction with Rules 1.04 and 2.03, which direct courts to secure the just, most expeditious and least expensive determination of proceedings on their merits.[7] The proper analysis is therefore a balancing approach that considers the entire factual context surrounding the late service.

In conducting that analysis, the Court considered the nature of the explanation for the delay, whether the delay was tactical, the significance of the proposed expert evidence, the degree of prejudice to the opposing party, the potential impact on the trial date, and the consequences of excluding the evidence altogether. In Pelrine, the court determined that the delay was not tactical, the reports had been served more than a year before trial, their admission would not disrupt the trial schedule, and the plaintiffs had ample opportunity to respond. Conversely, exclusion of the reports would have significantly impaired the defendant’s ability to advance his defence on important issues of causation and damages. In considering those factors, the Divisional Court found that excluding the reports was not proportionate to the procedural breach.

In reaching this conclusion, the Divisional Court followed its earlier decision in Harris v. Grand River Hospital, 2026 ONSC 240[8], which confirmed that Rule 53.08 must be applied with a balanced approach and having regard to the overall interests of justice.

The significance of Pelrine is that an imperfect explanation is no longer necessarily fatal under Rule 53.08. While the decision does not eliminate the requirement to provide a reasonable explanation for the failure to comply with the applicable deadline, it confirms that this requirement must be considered as part of the broader Rule 53.08 analysis. The Court must balance the explanation provided against the issues of prejudice, delay, tactical conduct and the overarching interests of justice.