It is against the law to not wear a motorcycle helmet while riding in California. All motorcycle riders and their passengers must wear Department of Transportation approved headgear. Helmets can drastically decrease the risk of serious and fatal head and brain injuries in a motorcycle accident. They could also impact a personal injury lawsuit after a crash. Failure to wear a helmet could become evidence against the plaintiff if he or she is attempting to obtain compensation for a related injury. An injury to the body and not to the head, however, may have nothing to do with whether the motorcyclist was wearing a helmet.