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work injury accident


If you have a pre-existing condition that was made worse by an accident, and you decide to sue, it is likely that an argument will be made that either the “thin skull” or “crumbling skull” rule applies. Your lawyer will advance the first principle; defence counsel will argue the second.


The well-known “thin skull” rule makes the defendant liable for the plaintiff’s injuries even if the injuries are unexpectedly severe as arising from a pre-existing condition. In applying this principle, the defendant is said to take their victim as they found them, pre-existing injuries and all, making them therefore fully liable for new, symptomatic, super-imposed or worsening injuries even though the nature and extent of the plaintiff’s injuries may be more substantial than otherwise foreseen.


Reality is everything. How has this person’s life been affected in terms of limitations, restrictions and functionality? What have they now lost that they couldn’t afford to lose? What has been taken away? For example, it might be said that a man who has already lost a hand cannot eat without the other one. The loss of his only hand is worth is a greater loss to him, everything considered.

On the other hand, the “crumbling skull” principle recognizes that a pre-existing condition was inherent in the plaintiff’s “original health condition” before an accident. It fails to consider the true nature and extent of the loss. This principle submits that the defendant need not put the plaintiff in a position that is better than their original position. No betterment is permitted.


The defendant is only required to pay the measurable difference. Via this principle, it could follow that while the defendant is liable for injuries caused, even if they are extreme, they need not compensate the plaintiff for any debilitating effects that are the direct result of the pre-existing condition which the plaintiff would have already suffered. Applying this principle, the defendant is liable for any additional damage, but not the pre-existing damage. In reducing the overall award, a judge may examine whether there was a measurable risk that the pre-existing condition could detrimentally affect the plaintiff in the future, regardless of the defendant’s negligence.

Both the thin skull and crumbling skull principles rely on a finding of facts as gathered, organized and decided by the trial judge. To determine which principle will apply, there will be an assessment of a measurable risk that the injury would or would not have occurred but for the accident. Is the new or worsening injury superimposed upon the old? Is a worsening injury such that it takes away what the Plaintiff cannot afford to lose? Has a worsening injury once been asymptomatic before the subject accident and symptomatic thereafter?


Only a Trial Judge’s discretion can be applied to answer this often complex, multi-factorial question. That said, an assessment of injuries should be considered through the Plaintiff’s eyes as against the full import and effect of the new, superimposed or worsened injuries against the full backdrop of the Plaintiff’s life, more fully appreciating the nature, importance and effect of the Plaintiff’s true losses in a real world.


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