A 'demurrer' is a pleading in a lawsuit that objects to an earlier pleading filed by an opposing party. The word 'demur' means to object; a 'demurrer' is the document that makes the objection. Typically, the defendant will demur to the complaint, but it is also possible for plaintiff to demur to an answer. The demurrer challenges the "legal sufficiency" of a claim, cause of action, or defense. If a cause of action in a complaint does not state a cognizable claim or if it does not state all the required elements, then the complaint can be knocked out with a demurrer. A demurrer is filed near the beginning of a case during the pleading phase.

At common law, a demurrer was the most common pleading by which a defendant would challenge legal sufficiency in criminal or civil cases, but today the pleading is abolished in many jurisdictions, including the federal court system (though some jurisdictions, including California and Virginia retain it). In criminal cases, a demurrer was considered a common law due process right, to be heard and decided before the defendant was required to plead "not guilty", or make any other pleading in response, without having to admit or deny any of the facts alleged.

A demurrer is not a challenge to the ultimate merits of a case or claim. When ruling on a demurrer, a judge is required by law to assume as true facts alleged in the complaint, even if those facts would later be challenged. Historically, however, a party filing a demurrer often had to admit the facts in the complaint and waive the right to later challenge those facts.

Overview