Legal grounds upon which a defendant may countersue a plaintiff if the plaintiffs lawsuit was totally frivolous and without any merit, and was brought simply to harass the defendant. To prove a case of malicious prosecution, the plaintiffs case must have been decided in favor of the defendant, and the defendant must show that there was no probable cause to believe that the defendant was liable and that the plaintiff (or plaintiffs attorney) acted with malice in bringing the suit. Given those restrictions, physicians have had very limited success in suing malpractice plaintiffs for malicious prosecution.