A plaintiff may only sue once in the court system for each case. He or she must bring forward the entire subject matter of the case at one time and claim every court remedy which flows out of the subject matter of the case. There is no opportunity to sue in a second lawsuit for something that was inadvertently or intentionally left out of the first lawsuit. The legal doctrine which prohibits more than one lawsuit for each case is called the doctrine of res judicata. Res judicata is a Latin phrase which means that “it has passed into a matter adjudged.” The plaintiff is “estopped” (stopped) from launching a second lawsuit.
The doctrine also applies to the defendant. He or she must bring forward every defence based on the subject matter of the plaintiff’s case at one time and any related counterclaim to the plaintiff’s claim.
The doctrine of res judicata is a fundamental doctrine of the justice system in Canada and it is based on two traditional policy considerations: firstly, the ground of public policy that it is in the interest of the public that an end be put to litigation, and secondly, the ground of individual right that no one should be twice vexed by the subject matter of the lawsuit. Other considerations include the courts’ scarce resources and the additional financial burden to the litigants.