An assertion by the defendant that although the facts alleged by the plaintiff in the complaint may be true, they do not entitle the plaintiff to prevail in the lawsuit.
The pleadings of the parties to a lawsuit describe the dispute to be resolved. The plaintiff sets out the facts that support the claim made in the complaint, and the defendant then has an opportunity to respond in an answer.
A demurrer is a type of answer used in systems of code pleading, established by statute to replace the earlier common-law forms of action. While a demurrer admits the truth of the plaintiff's set of facts, it contends that those facts are insufficient to grant the complaint in favor of the plaintiff. A demurrer may further contend that the complaint does not set forth enough facts to justify legal relief or it may introduce additional facts that defeat the legal effectiveness of the plaintiff's complaint. A demurrer asserts that, even if the plaintiff's facts are correct, the defendant should not have to answer them or proceed with the case.
Under the modern rules of pleading established by the rules of federal civil procedure and followed in a number of states, the demurrer has been abolished as a formal type of answer. The same argument against the plaintiff's cause of action can be, however, made by motion to dismiss the plaintiff's action on the ground that he or she has failed to state a claim on which relief can be granted. Even where the formal demurrer is no longer used, lawyers and judges often use the old term for an argument of the same type.