By: Tatianna Macdonald (Associate Lawyer) and Paul Papaeliou (Articling Student)
In MacNeill v. McDonald’s Restaurants of Canada Limited, 2025 ONSC 3780, the Ontario Superior Court delivered a pointed reminder that causation cannot rest on inference alone, particularly where pre-existing impairments account for a plaintiff’s limitations. Justice McCarthy dismissed the majority of Ms. MacNeill’s $1.8 million claim, awarding just $5,000 in general damages after finding her injuries were transient and her long-standing impairments remained the true drivers of her condition.
The plaintiff alleged that she suffered chronic throat injury, muscle tension dysphonia (“MTD”), and related psychological deterioration after ingesting a small quantity of delimer solution through a coffee cup served at a McDonald’s drive-thru in Orillia. While liability for the incident was admitted, damages and causation were contested. At trial, the plaintiff advanced claims under five heads of damages, including general damages of up to $125,000, more than $1.4 million in alleged income loss, and over $200,000 in future care. She maintained that her voice condition rendered her unemployable and caused permanent functional limitations. However, Justice McCarthy found these assertions inconsistent with the medical evidence, her own conduct, and her extensive pre-incident history.
Justice McCarthy rejected the plaintiff’s position in full, concluding that any symptoms arising from the delimer ingestion were temporary and non-disabling. The ingested product was a citric acid-based solution with a pH comparable to lemon juice and contained no caustic agents such as phosphoric or nitric acid. Expert evidence confirmed that no health injuries are expected from ingestion under normal use, and hospital records revealed no burns, swelling, or mucosal damage.
The judge accepted that the plaintiff may have experienced nausea and mild throat discomfort, but found these effects resolved quickly. Beyond the day of the incident and perhaps a short period afterward, the evidence did not support any continuing physical injury attributable to the event. “[A]ny pain in her throat or oral cavity and any disruption in her voice quality caused by the ingestion… would have subsided,” he wrote.
Justice McCarthy dismissed the plaintiff’s ongoing voice issues as more plausibly caused by unrelated, long-standing factors such as chronic acid reflux, smoking, and vocal overuse. The court preferred the evidence of defence ENT Dr. Werger, who found no objective signs of injury years later and noted the absence of any mucosal trauma in the immediate post-incident records.
Pre-Existing Issues Drove the Outcome
The most damaging element to the plaintiff’s case was her documented history of significant pre-existing health issues, both physical and psychological, dating back to a 2009 motor vehicle collision. That collision had previously been the subject of litigation, with her own experts concluding she suffered from permanent impairments and was “basically unemployable.” She returned to work in 2015 for Nordia in a call centre role, one of the few options open to her given her physical restrictions, but only after years of inactivity. Her pre-incident employment history was described by the court as “sporadic and brief.”
Justice McCarthy found the plaintiff’s evidence lacking in candour. He noted her tendency to overstate her postincident symptoms while minimizing her pre-existing difficulties brought about credibility issues. She failed to disclose key facts to her treating providers and expert witnesses, including her prior diagnoses and the chemical composition of the ingested substance. Expert opinions that sought to draw a causal line between the delimer ingestion and her ongoing disability were critically undermined by these omissions.
The court also highlighted inconsistencies in the plaintiff’s own conduct. Despite claiming disabling symptoms, she failed to follow through with recommended voice therapy, declined to explore funding options, and ultimately told one of her treating ENTs that she had no interest in returning to work as ODSP payments exceeded her potential part-time earnings.
Implications
This case stands as a stark reminder that causation must be grounded in reliable, complete, and credible evidence. A plaintiff with extensive pre-incident health issues who claims new impairments must show more than post-incident deterioration. They must demonstrate that, but for the incident, the current condition would not exist. Here, Ms. MacNeill failed to bridge that gap. The ingestion event, while unfortunate, produced at most a minor and short-lived injury. Her long-standing, well-documented, and functionally limiting history remained the true cause of her ongoing impairments.
Justice McCarthy’s judgment reinforces that courts will not award substantial damages based on speculative or exaggerated claims, particularly where pre-existing impairments remain inseparable from the plaintiff’s present limitations.