Contributory negligence is a common law tort rule (created by judges in court opinions, judicial decisions, or case law) that bars or prevents a plaintiff from recovering on a claim for negligence if the plaintiff contributed to the cause of the accident (was contributorily negligent) in any way. This rule may be referred to as pure comparative negligence.

Some states still apply the contributory negligence rule. But because of the harsh outcome of the contributory negligence rule, many state legislatures have enacted statutes that provide for comparative negligence or fault and reduce the plaintiff’s recovery by the amount of the plaintiff’s negligence or fault. This rule may be referred to as pure comparative fault.

Other states have enacted a modified comparative fault statute or law that reduces a plaintiff’s recovery by the plaintiff’s percentage of fault, but bars a plaintiff from any recovery if the plaintiff is 50% or more at fault for the cause of the accident.

And in South Dakota, the comparative fault system uses a slight/gross negligence system and only analyzes the comparative fault if the plaintiff’s negligence is slight and the defendant’s negligence is gross. Under this slight/gross negligence system, if the plaintiff’s negligence is more than slight and the defendant’s negligence is less than gross, the plaintiff is barred or prohibited from any recovery.

These contributory negligence and comparative fault laws vary from state to state and may change or evolve at any time—whether they are located in court opinions or in statutes.

In Washington (WA), the rule of pure comparative negligence applies. Under this system, a plaintiff's recovery is reduced by their own percentage of fault. However, unlike contributory negligence, which bars recovery if the plaintiff is at all responsible, comparative negligence allows a plaintiff to recover damages even if they are found to be 99% at fault, with the recovery amount being reduced accordingly. Washington does not follow the harsher contributory negligence rule that completely bars recovery if the plaintiff has any degree of fault, nor does it follow the modified comparative fault approach that bars recovery at a certain threshold of plaintiff's fault (such as 50% or more). Washington's approach is more lenient towards plaintiffs, allowing them to recover some damages as long as they are not solely responsible for the incident.