In common law, a demurrer was the pleading through which a defendant challenged the legal sufficiency of a complaint in criminal or civil cases.
For example, the court can take judicial notice of commonly known facts not reasonably subject to challenge, such as the Gregorian calendar, or of public records, such as a published legislative report showing the intent of the legislature in enacting a particular statute.
Rather, a demurrer is a particular type of pleading and demurring is the act by which a party formally requests the court to dismiss a cause of action (claim) or the entire complaint.
In lay terms, a judge who sustains a demurrer is saying that the law does not recognize a legal claim for the facts stated by the complaining party.
If the demurrer is overruled, the defendant is ordered to file an answer within a certain period of time or else risk a default judgment.
Demurrers sustained with prejudice are reserved for when the judge determines a plaintiff cannot cure or fix the complaint by rewriting or amending it.
In criminal cases, a demurrer may be used in some circumstances to challenge the legal sufficiency of the indictment or other similar charging instrument.
While there are different ways to accomplish the goals of a special demurrer, often an alternative method to challenge the sufficiency of the indictment is an attack on the prosecution's case prior to trial, and is generally made by means of motion to dismiss.
It has been superseded by the more modern motion to quash, usually a verbal application to the judge to rule the indictment null and void and to stop the case.
Although the demurrer technically also framed the issues in a case, treating the demurrer as a pleading came to be seen as irrational because it was the only pleading that required an immediate hearing and ruling on its content (which consisted of an attack upon the complaint), while the complaint and the answer merely stated the respective positions of each side but did not require hearings in and of themselves.
Thus, it made sense that a discretionary attack upon the complaint that was already being drafted, calendared, heard, and ruled upon like a motion should simply be treated like one.
In California, a demurrer must assume the truth of the facts alleged by the complaining party, but challenges the complaint as a matter of law.
[9] The term preliminary objection is used in Pennsylvania state court to refer to all motions made after the filing of a complaint but before the filing of an answer; preliminary objections may be made "in the nature of a demurrer" (seeking to dismiss a cause of action for legal insufficiency) or "in the nature of a motion to strike" (seeking to remove parts of a pleading for failure to abide by the technical rules), as well as various other means.