Fault

In law, fault means responsibility for causing an injury or loss. Most personal injury and property claims are fault-based: the injured person must show that someone else was at fault, usually through negligence (failing to use reasonable care) or intentional wrongdoing. Some claims, such as strict liability for defective products, do not require proof of fault in the usual sense.

Fault is often shared, and states handle that differently. Under pure comparative negligence, an injured person who was 99% at fault can still recover 1% of their damages; under modified comparative negligence, recovery is barred once the person's share reaches 50% or 51%, depending on the state. A few jurisdictions still follow contributory negligence, which can bar recovery entirely if the injured person was even slightly at fault. Some federal laws have their own rules; for example, the Federal Employers' Liability Act for railroad workers reduces damages in proportion to the worker's own negligence rather than barring them.

Fault also shapes car insurance. In "at-fault" states, the driver who caused a crash and their insurer pay for the other driver's losses. In no-fault states, each driver's own personal injury protection pays first, regardless of who caused the crash, and lawsuits are limited to more serious injuries.

In class actions, fault is usually a common question, such as whether a company's policy was unlawful, rather than an individual one. That is why most consumer class actions focus on uniform practices. For insurance disputes where fault matters, see our pages on underinsured motorist stacking and total loss car payouts.