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Glossary

Causation

The link between someone's careless act and your injury. You must show the crash caused the harm you are claiming.

Last reviewed By the Editorial team 2 min read

General information, not legal advice. Talk to a licensed attorney in your state.

Quick answer

Causation is the link between a careless act and the harm it did. In an injury claim, you must show that the other driver's conduct caused the crash, and that the crash caused the injuries and losses you are claiming. Courts look at two parts: actual cause and proximate cause.

In a car accident claim#

Causation is one of the elements of a Negligence. Failing to use the care a reasonable person would use in the same situation, such as running a red light or texting while driving. Glossary claim, along with a duty, a breach of that duty and damages. The car accidents guide walks through all four. Actual cause asks whether the harm would have happened without the careless act. Proximate cause, in the words of Cornell's Legal Information Institute, is "an actual cause that is also legally sufficient to support liability."

The fault part is often clear in a rear-end crash. The harder fight is usually about injuries. Insurers may argue that pain came from an old condition, a later event or something else entirely. Records made soon after the crash, doctors' opinions and a steady treatment history are the usual proof. When a crash makes an earlier condition worse, the Eggshell plaintiff rule. The rule that a person who causes an injury is responsible for all the harm it does, even if the injured person was unusually fragile, for example because of an old injury or an illness. Glossary rule and the line between old and new harm come into play; see back and neck injuries and the injuries hub.

Example#

Questions people ask

What is the difference between actual cause and proximate cause?

Actual cause means the harm would not have happened without the act. Proximate cause adds a legal limit: the harm must be a close enough result of the act for the law to hold the person responsible.

Who has to prove causation?

The person making the claim. In civil cases, the plaintiff generally has the burden of proving their case, including that the crash caused the injuries.

Sources

  1. Cornell Law School, Legal Information Institute, Wex: proximate cause — actual and proximate cause
  2. Cornell Law School, Legal Information Institute, Wex: negligence — the elements of a negligence claim
  3. United States Courts, Glossary of legal terms — burden of proof

Last reviewed October 29, 2026 by the Accident Claim Facts editorial team. Found an error? Tell us.

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