Assumption of risk is a defense in the law of torts, which bars or reduces a plaintiff's right to recovery against a negligent tortfeasor if the defendant can demonstrate that the plaintiff voluntarily and knowingly assumed the risks at issue inherent to the dangerous activity in which he was participating at the time of his or her injury.
What is usually meant by assumption of risk is more precisely termed primary or "express" assumption of risk. It occurs when the plaintiff has either expressly or implicitly relieved the defendant of the duty to mitigate or relieve the risk causing the injury from which the cause of action arises. It operates as a complete bar to liability on the theory that upon assumption of the risk, there is no longer a duty of care running from the defendant to the plaintiff; without a duty owed by the defendant, there can be no negligence on his part. However, primary assumption of risk is not a blanket exemption from liability for the operators of a dangerous activity. The specific risk causing the injury must have been known to, and appreciated by, the plaintiff in order for primary assumption of risk to apply. Also, assumption of risk does not absolve a defendant of liability for reckless conduct.
This defense is commonly asserted in cases of injuries occurring during risky recreational activities, such as skiing, paragliding, and scuba diving, but actually extends to all dangerous activities. Thus, for example, it was held that a visitor to the Burning Man festival assumed the risk of getting burned.
Secondary assumption of risk is a rather different doctrine akin in some respects to comparative negligence. The difference was explained by the Supreme Court of California as follows: