How Does a Pre-Existing Injury affect a Plaintiff's Claim for Damages? New case law in New Brunswick provides guidance.
Published:
9 avril 2026
Author(s):
In personal injury cases, how does New Brunswick tort law treat plaintiffs with a history of medical and psychological issues? Do pre-existing conditions limit a plaintiff’s ability to sue for damages? A recent decision by the New Brunswick Court of Appeal has provided clear guidance on how these questions should be handled.
Quantifying personal injury damages has proven to be a point of difficulty for courts, insurers and counsel, especially in cases involving a wide range of symptoms. Plaintiffs often present with a constellation of issues—soft tissue injuries, concussions, chronic pain disorders, and preexisting psychological vulnerabilities—that complicate the assessment of both causation and damages. The courts must reconcile complex medical evidence with foundational legal principles, including foreseeability and factual versus legal causation.
The New Brunswick Court of Appeal’s analysis in Trainor v. DeArcos, 2025 NBCA 139, revisits and reinforces the principles governing causation and the treatment of preexisting conditions in assessing pecuniary damages. When read alongside Vincent v. AbuBakare, the seminal NBCA decision on loss of earning capacity, Trainor provides guidance for assessing personal injury damages in cases involving complex medical and psychological histories.
Plaintiff Injuries & Trial Decision
The appellant, a 20-year-old woman, was injured in a motor vehicle accident while riding as a passenger. The appellant suffered multiple injuries, including:
A broken heel bone
A hairline hand fracture
Chest bruising
Chronic pain
PTSD and anxiety
Temporomandibular disorder (TMD)
The defendant admitted liability; however, there was a significant dispute over the scope of the injuries, causation, and the appropriate quantum of damages.
Prior to the accident, the appellant had a well-documented psychological history including dyslexia, dyscalculia, major depression, anxiety, ADD, and borderline personality disorder. She had also undergone corrective leg surgery. After the accident, her chronic pain and mental health conditions intensified.
Despite accepting factual causation for several injuries, the trial judge concluded that the chronic pain, TMD, and subsequent leg surgeries were not reasonably foreseeable consequences of the collision. The judge alternatively applied the crumbling skull doctrine to bar recovery for these injuries, and in doing so also applied a 40% discount to the appellant’s future earning capacity damages.
The Appeal
The appeal centered on three issues: (1) the proper test for legal causation, (2) the correct application of the crumbling skull and thin skull doctrines, and (3) the appropriateness of the 40% discount applied to the appellant’s future income loss.
A. Foreseeability and Legal Causation
A central theme in Trainor is the reaffirmation that legal causation is a question of law, not medicine. While factual causation concerns whether the defendant’s actions caused the plaintiff’s injuries, legal causation asks whether the type or “genus” of injury was reasonably foreseeable.
1. Objective Foreseeability: The “Person of Ordinary Fortitude” Standard
The Court of Appeal held that the test of foreseeability was whether a defendant could reasonably foresee damages suffered by a person of ordinary fortitude. In this case, could injuries such as chronic pain, TMD, or further leg complications be a foreseeable outcome for a person of normal psychological and physical resilience? The Court of Appeal found that the trial judge erred by focusing on the appellant’s subjective vulnerabilities rather than applying the correct objective standard.
The trial judge placed significant weight on medical evidence discussing the appellant’s psychiatric profile and its alleged relationship to her chronic pain. The foreseeability inquiry does not depend on whether this particular plaintiff would suffer chronic pain. Instead, the question is whether such injuries are a reasonably foreseeable consequence of the accident.
The Court followed caselaw from British Columbia where similar injuries were found to be recoverable in motor vehicle accidents; as a result, it set aside the trial judge’s finding that the chronic pain, TMD and additional surgeries were not foreseeable.
2. Conflation of Factual and Legal Causation
Evidence must establish both factual and legal causation. Factual causation requires proof that the defendant’s actions caused the plaintiff’s injuries, while legal causation requires that the injuries be a reasonably foreseeable consequence of the defendant’s actions.
The Court of Appeal found that the trial judge improperly relied on factual causation principles—such as the “but for” test—when evaluating legal causation. For example, in assessing foreseeability of the leg surgeries, the trial judge noted that a physician had not stated the surgeries would not have occurred “but for” the accident. This analysis is reserved for factual causation, whereas the proper legal question is whether such surgeries were within the range of foreseeable outcomes of the accident. The question of legal causation is a legal determination to be made by the trier of fact, and not a matter of medical expertise.
By applying the wrong standard, the trial judge improperly excluded chronic pain, TMD, and postaccident surgeries from the compensable injury list.
3. Case Precedents and Legal Doctrines
The Court of Appeal aligned its analysis with the Supreme Court of Canada’s decision in Mustapha and the BCCA’s reasoning in Greenway-Brown, confirming that soft tissue injuries leading to chronic pain and psychological complications are foreseeable outcomes of motor vehicle accidents—even in plaintiffs with preexisting vulnerabilities.
Accordingly, the findings on legal foreseeability were set aside.
B. Crumbling Skull vs. Thin Skull: Correcting the Doctrinal Errors
The Court of Appeal affirmed the trial judge’s articulation of the two doctrines but rejected her application of them.
1. Thin Skull Doctrine
A thin skull plaintiff must be taken as they are found. If a plaintiff has stable preexisting vulnerabilities that make injuries worse, the defendant remains fully liable.
2. Crumbling Skull Doctrine
A crumbling skull plaintiff has a preexisting condition that would have deteriorated regardless of the accident. In such cases, damages may be reduced to reflect the hypothetical decline.
3. The Trial Judge’s Contradictions
The Court identified a contradiction in the trial judge’s reasoning:
On one hand, the judge concluded that the plaintiff’s chronic pain originated from her preexisting psychological conditions.
On the other hand, she acknowledged that those conditions were “well managed” and merely increased the appellant’s vulnerability.
If the preexisting conditions were stable and well controlled, the appellant cannot be a crumbling skull plaintiff. Instead, she fits squarely within the thin skull doctrine: the accident caused real injuries that were exacerbated by preexisting conditions.
4. Crumbling Skull Does Not Bar Recovery
The Court also corrected the trial judge’s suggestion that the crumbling skull doctrine precludes recovery. It does not. Rather, it reduces damages where deterioration would have occurred independently of the accident.
Because the trial judge found the appellant’s conditions were well managed, the appellate court held that she erred in applying the crumbling skull doctrine at all.
The appellant was properly characterized as a thin skull plaintiff, warranting the application of provisional damages. The trial judge’s decision included provisional assessments in the event that she was mistaken on her findings of causation or application of the crumbling skull doctrine. The Court of Appeal upheld the provisional assessment by the trial judge, holding that the appellant was best characterized as a thin skull plaintiff.
C. The 40% Discount on Future Earning Capacity Damages
The trial judge applied a 40% reduction to the appellant’s future earning capacity assessment, reasoning that the appellant’s preexisting psychological conditions would have eventually impaired her capacity to work. However, this discount was based on a misapprehension of the evidence.
1. Inconsistent with Other Findings
The trial judge accepted that the appellant would have continued working and reintegrated into the workforce before trial yet simultaneously applied a 40% reduction for future vulnerability. These findings are inconsistent.
2. Misapprehension of Actuarial Evidence
The trial judge also stated that the actuary had not accounted for general disablement rates. The Court of Appeal, upon reviewing the record, found that this was incorrect—the actuary had explicitly accounted for these contingencies.
Based on these errors, the 40% discount was entirely withdrawn.
D. General Damages: A Shift in New Brunswick
New Brunswick’s prior upper range for general damages in personal injury cases involving multiple injuries or brain trauma was approximately $125,000 to $150,000. However, Trainor v. DeArcos marks a significant shift.
The trial judge had provisionally assessed general damages at $200,000. Although she reduced this amount in her final award, the Court of Appeal reinstated the full provisional assessment.
The appellant was therefore awarded $200,000 in general damages, reflecting:
Chronic pain
Fractures
PTSD
TMD
Conclusion: Implications for New Brunswick Insurance Law
Trainor v. DeArcos is a pivotal development in New Brunswick’s personal injury jurisprudence. It clarifies the correct approach to legal causation, underscores the distinction between thin and crumbling skull plaintiffs, and clarifies the analysis on future earning capacity damages.
Related Lawyers
Services Connexes
