After a complaint has been filed against a defendant for damages or other orders of the court, the defendant may file a written complaint against the party suing him/her or against a third party as long as the subject matter is related to the original complaint. the defendant’s filing of a complaint is called a cross-complaint, and the defendant is then called a cross-complainant and the party he/she sues is called a cross-defendant. the defendant must still file an answer or other response to the original complaint. if the cross-complaint is against the original plaintiff (original suer) then it can be served on the plaintiff’s attorney by mail, but a third party must be served in person with the cross-complaint and a new summons issued by the clerk of the court. the cross-defendants must then file answers or other responses. these are called pleadings and must be carefully drafted (usually by an attorney) to properly state the factual as well as legal basis for the claim and contain a prayer for damages or other relief.