Causation – What came first, the accident or the illness?

Causation – What came first, the accident or the illness?

In order to successfully litigate a motor vehicle accident tort claim, it is not enough to prove that the “at fault” driver collided with your vehicle, or did something negligent on the road that resulted in an accident. It is also necessary to prove that the negligence of the other driver caused your injuries and subsequent medical problems – causation.


This is the concept of causation, which is fraught with complexities given that most accident victims are not 21-year-old athletes that have never had an injury or illness in their lifetime. Most motor vehicle accident victims have a history of health issues and underlying health problems that have affected them at one time.

The “thin skull principle” of causation, which has developed in our law, makes the “at fault” driver liable for your injuries even if the injuries are unexpectedly severe owing to a pre-existing condition. Where the negligent conduct of an “at fault” driver “materially contributes” to the occurrence of the post accident problems, the “at fault” driver may be found liable for all of the injuries sustained as a result of the motor vehicle accident.

Thin Skull Plaintiff

Essentially, a “thin skull plaintiff” is someone who has a latent, pre-existing condition or vulnerability to injury that is brought to the fore by the motor vehicle accident and that would not have presented itself had the accident not occurred. So for example, someone who suffered abuse as a child may be more fragile psychologically and more vulnerable if they suffer an adverse life event. Accordingly, such a person might be more likely to suffer more severe depression as a result of a motor vehicle accident that appears to have been minor. Had the accident not occurred, this person may never have experienced severe depression.

Crumbling Skull Plaintiff

This is to be distinguished from the “crumbling skull” plaintiff which is someone who has a pre-existing illness or medical condition that would have come to the fore even if the accident had not occurred. For the “crumbling skull” plaintiff the accident may, however, have accelerated the presentation or evolution of the illness or medical condition and this may entitle that person to some measure of compensation in the appropriate circumstances.

If it cannot be established that the motor vehicle accident caused or contributed to the plaintiff’s condition, which would have remained the same even if the accident had not occurred, causation will not be established and no compensation can be recovered.

Medical evidence is essential in establishing causation and treatment providers and medical experts are often called upon to address this issue. Since there are often multiple causes for a person’s inability to function post accident, navigating through the medical minutiae and advocating effectively for the injured party becomes the task of the personal injury lawyer.

Motor vehicle accident law is a very specific area of the law and it is important to consult legal practitioners who have the necessary expertise to analyze the medical evidence and legal issues in order to ascertain the viability of your claim.

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