Causation in injury claims
In plain English: causation is the link between what the other person did and the harm you suffered. It isn't enough to show they were careless. You also have to show their carelessness caused your injuries and losses.
The two questions courts ask
Factual causation. Would the harm have happened anyway? This is usually called the "but for" test: but for the defendant's carelessness, would you have been injured? If the answer is no, factual causation is usually met.
Legal causation. Is the harm too remote or unforeseeable to hold them responsible for? US courts call this proximate cause. In the UK and Canada it is usually discussed as remoteness. Most accident injuries pass easily, but unusual chains of events can fail here.
Where insurers push back
- Delay in treatment. If you first saw a doctor three weeks later, the insurer will suggest something else happened in between.
- Low-speed collisions. Insurers often argue minor vehicle damage means no real injury was possible. Medical evidence, not the repair bill, should decide this.
- Pre-existing conditions. An old back problem or earlier whiplash will be blamed for your current symptoms.
- Later events. A second accident, a sports injury or a fall after the crash can muddy which event caused what.
Pre-existing conditions and the eggshell rule
A defendant takes you as they find you. If you had a fragile spine and a crash that would bruise most people causes you a disc injury, the defendant is usually responsible for the full injury. This is often called the eggshell skull or thin skull rule, and it applies in the US, UK and Canada.
There is a limit, though. If your condition was already getting worse and would have caused problems anyway, compensation may be reduced to reflect that. Courts sometimes call this the crumbling skull argument. The fight is usually about how much of your current state is down to the accident and how much would have happened regardless.
You had occasional knee pain but never missed work. After a slip in a supermarket you need surgery. The store's insurer argues arthritis caused it. Your GP records showing no treatment for two years before the fall, followed by a surgeon's report linking the tear to the fall, are what answer that argument.
How to strengthen the link
- See a doctor promptly and describe the accident clearly.
- Be upfront about earlier injuries so your doctor can explain what changed.
- Keep treatment consistent and note the reasons for any gaps.
- In serious cases, ask your lawyer whether a specialist causation report is needed.
Next: expert witness · medical records · burden of proof.
Related terms
General information, not legal or medical advice. Rules differ between US states, the UK and Canadian provinces, so check the law where your accident happened. How we write and check · Legal disclaimer