When two or more parties are jointly and severally liable for a tortious act, each party is independently liable for the full extent of the injuries stemming from the tortious act. Thus, if a plaintiff wins a money judgment against the parties collectively, the plaintiff may collect the full value of the judgment from any one of them. That party may then seek contribution from the other wrong-doers. This concept of choosing the defendant(s) from whom to collect damages is called the law of indivisible injury.
The issue of joint and several liability is often involved in "toxic torts" claims, such as cases involving asbestos-related mesothelioma. This is because mesothelioma can be caused by exposure to asbestos, but often times workers exposed to asbestos had faced exposure in multiple jobs on multiple job sites, and so it is difficult to pick a single tortfeasor responsible for the resulting mesothelioma.
For example suppose that A, B, and C negligently injure V. V successfully sues A, B, and C, for $1,000,000. If the court used a joint and several liability system, V could demand that A pay V the full $1,000,000. A could them demand contribution from B and C. However, if B or C could not pay, A would be stuck paying the full $1,000,000.
Risk Reduction and Liability Reduction
Joint and several liability reduces plaintiffs' risk that one or more defendants are judgment-proof by shifting that risk onto the other defendants. Only if all defendants are judgment-proof will a plaintiff be unable to recover anything. However, this system can cause inequities, particularly where a relatively blameless defendant is forced to bear the financial burden of an incredibly guilty co-defendant's insolvency.
The court in Ford Motor v. Boomer (2003) investigated the issue of liability reduction, and found that when two tortfeasors are liable for one incident (i.e. two negligent drivers were involved in a car accident), but the court cannot determine which tortfeasor is more responsible and to what degree, then the the court may lessen the liability of both or either tortfeasor.
There is another type of joint and several liability called market share liability. This doctrine is invoked when a good causes an injury, and there are multiple manufacturers of the good. When a court cannot determine which manufacturer created the precise good which caused the harm, the manufacturers will be held proportionately liable in accordance with their market share in the market of the good. Sindell v. Abbott Laboratories (1980) helped to develop this doctrine.
Another type of joint and several liability is called the doctrine of alternative liability. Summers v Tice (1948) contributed to the doctrine when the court found that under the doctrine of alternative liability, two independent tortfeasors may each be held liable for the full extent of the plaintiff's injuries if it is impossible to tell which tortfeasor caused the plaintiff's injuries. The burden of proof will shift to the defendants to either absolve themselves of liability or apportion the damages between themselves. If the defendants, however, are acting in concert with each other, then the doctrine would not apply, because then both Ds would be responsible regardless of who pulled the trigger
A third variety is typically referred to as either "preempted causes" or "doomed plaintiffs." Dillon v. Twin State Gas & Electric Co (1932) helped to develop this doctrine. In the case, a boy was playing on a bridge when he lost his balance and fell from the bridge; but he was fatally electrocuted when he tried to steady himself by grabbing a nearby high voltage wire. The court found that because the boy would have probably died anyway in falling from the bridge, the defendant (electrical company which maintained the electrical wires) should not be held liable for any damages except those that would compensate for the increase in boy’s suffering due to electrocution.