THE THIN SKULL RULE

There is a long standing principle of law, known to veteran medical legal report writers as the “thin skull” rule. Simply put, the rule is “you take the victim as you find her”. This principle makes the at fault defendant liable for the plaintiff’s injuries even if the injuries are unexpectedly severe for that individual, owing to a pre-existing condition. Causation is determined based on the particular characteristics of the individual.

THE CRUMBLING SKULL RULE

There has been another long standing principle of law, less well known to report writers called the “crumbling skull” rule. This principle is intended to differentiate cases where what you see is similar to what you would have expected without the intervening trauma of this accident. In the case of the application of this principle, the person would have to have been either deteriorating or expected to deteriorate to the same extent as is now evident and in the same period of time, even without this new intervening traumatic event, in order to exclude their recovery. Only if the thing claimed for would probably have occurred at the same time and to the same extent without the accident, does this principle apply.

THE THIN SKULL RULE REVISITED

In an important decision of the Supreme Court of Canada, decided in 1996, they reviewed these principles to look again at what role a motor vehicle accident has to play in the person’s condition in order for the condition to be considered “caused or contributed to by the accident” and therefore, be compensable.

The Supreme Court of Canada held that a defendant is liable for any injuries caused or contributed to by his or her negligence. The presence of other non-tortious contributing causes does not reduce the extent of that liability. There is to be no apportioning between the accident and other causes. Causation is established where the defendant’s negligence “materially contributed” to the occurrence of the presenting problem. The defendant is still 100% liable even where there are other causal factors which helped produce the condition.

On the particular facts of the case being decided by the Supreme Court of Canada, the trial judge held that the accident contributed 25% to the plaintiff’s condition and that was held by the appeal court to be “material”. Once there is a material contribution, the plaintiff is entitled to recover full damages. Once it is proven that the defendant’s negligence was a cause of the injury, there is no reduction of the award to reflect the existence of other non-accident related causes. As long as a defendant is part of the cause of an injury, the defendant is liable, even though his act alone was not enough to create the injury. Expressed in reverse, even if the accident played a minor role, the defendant is still fully liable if the accident was a necessary contributing cause of the present condition.

THE THIN SKULL RULE EXPANDED

These principles have been further considered in a recently reported decision of the Ontario Court of Appeal from May 1998. In that case, the plaintiff had a pre existing psychological and emotional condition, sustained a brain injury in a car accident, and then had subsequent assaults which it was alleged by the defence caused the brain injury or contributed to its severity and effect. The court held that if the plaintiff’s condition resulted from the cumulative effect of the injuries sustained in the motor vehicle accident, the assaults and her pre-existing psychological condition, she would nonetheless be entitled to full compensation so long as the judge or jury was satisfied on a balance of probabilities, that the injuries sustained in the mva materially contributed to her overall condition. The fact that the plaintiff’s overall condition was exacerbated by subsequent assaults did not relieve the defendant from full responsibility.

This case law has very important implications for report writing by experts and their recommendations for rehabilitation. There has been a body of opinion in the past that the plaintiff is only entitled to be compensated in the proportion that the accident contributed to his injury. This line of thought has been overruled by these high court decisions. Failure to consider the concept of material contribution and minor but necessary role of the accident can deprive your patient of entitlement to compensation and important rehabilitation.

IMPLICATIONS FOR YOUR MEDICAL LEGAL REPORTS

In my opinion, the implications of these developments are as follows:

• If the plaintiff’s pre-accident intellectual, cognitive or behavioural functioning or environment make the effects of this injury more severe for her than for an average or higher functioning individual, she is entitled to be fully compensated for the effects of the injury on her. Causation is established in relation to each individual, not the average person.
  
  
• If the accident neither caused or contributed to the plaintiff’s condition and you believe that his situation would be exactly the same if the accident had never happened, then causation is not established and that patient is not entitled to recover for that particular condition.
  
  
• Even if the accident alone was not sufficient to create the plaintiff’s plight, if it played a necessary, even if minor, role, causation is established, and the plaintiff is entitled to be fully compensated and rehabilitated.
  
  
• Even if the plaintiff’s condition was the cumulative effect of several causes, only one of which was the accident, as long as the accident injuries materially contributed to the overall condition, the plaintiff is entitled to full (not just for the proportion caused by the accident) compensation and rehabilitation.