A legal theory, most often used in cases of tort (esp. negligence), allowing multiple contributors to a tort to be held liable, even if it cannot be proved which defendant's action was the proximate cause of the injury. Without joint and several liability, a defendant could avoid liability by claiming that the other tortfeasors were just as responsible for the injury, and that the injury would not have happened but for the actions of those other tortfeasors; each of the tortfeasors would be able to claim this, thus preventing the plaintiff from recovery. With joint and several liability, however, the defendents may be held liable as a group, preventing this loophole.