If you are in an accident that aggravates a pre-existing injury, that “old” injury can have varying effects on the potential settlement you could receive.
Personal injury law aims to put you in the position you were in before you were injured. At the onset of your claim, you must disclose any previous injuries. Once the claims process begins, there will likely be a lengthy discussion with opposing counsel (the insurance company) about the severity of any injuries you had before the accident.
This brings us to two important legal principles: the Thin Skull Rule and the Crumbling Skull Rule.
The Thin Skull Rule
The Thin Skull Rule means that the person who injured you is liable for your injuries, even if those injuries are unexpectedly severe because you had a prior condition. In Athey v. Leonati,  3 S.C.R. 458, the court determined that the person who injured you does not need to be the sole cause of your injury, as long as their negligence contributes to the injury.
Take the following as an example. Joe slipped on ice while walking on Tim’s property. The ice was there because Tim was negligent and didn’t salt the walkway. From this slip, Joe has a herniated disc in his back. Joe had previous back problems, but those weren’t bothering him at the time of the fall. Since Tim’s negligence caused the fall, and Joe’s previous injury was under control before the incident, Tim is fully liable for the resulting herniated disc.
Now, let’s look at the Crumbling Skull Rule.
The Crumbling Skull Rule
The Crumbling Skull Rule applies when you have a deteriorating pre-existing condition. The person who injured you is not responsible for the injuries you would have experienced anyway because of your degenerating condition. As summarized in Wallace v. Thibodeau, 2008 NBCA 78, the Crumbling Skull Rule is applied where the wrongdoer’s negligence causes problems associated with a previous degenerating condition. The courts reduce your damage award to reflect the possibility that the previous condition could have eventually caused the injury even if you weren’t in an accident. However, it is important to note that it is the wrongdoer’s responsibility to prove that you had a crumbling condition.
Remember the purpose of personal injury litigation described above? Well, the Crumbling Skull Rule is a way of ensuring the law meets this goal. It is effectively designed to limit a wrongdoer’s liability to a specific part of an injury, and not put you in a better position than you would have been if the accident didn’t happen. If the wrongdoer worsens the initial condition, they may be liable for damages for the fast-tracked progression. Still, they will not be liable for the injury specifically, as it would have eventually occurred regardless.
Take the above example with Joe and Tim. Say Joe’s pre-existing condition was Sciatica (a condition known to cause herniated discs), and he already knew that he would eventually have a herniated disc. Here, Tim would not be liable for causing the herniated disc, because Joe would have experienced this regardless of the incident. However, Tim may be responsible for damages for accelerating the herniated disc’s onset.
Regardless of the principles at play, we are here to help
As you can see, the intricacies of different potential legal principles at play in your personal injury claim can become rather complex. Whether your claim involves the Thin Skull Rule, the Crumbling Skull Rule, or some other legal principle not discussed here, it is important to seek legal advice to understand your claim. Doing so will ensure that the right legal principles are applied to your claim.
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