What is a Defense?
Defense, in law, the grounds asserted by the defendant for his not being liable when sued in a civil action or when prosecuted in a criminal case. The term is sometimes used to describe the strategy or tactics employed by the defendant's attorney, and also as a substitute for the term "defendant", as in the expression "attorney for the defense."
A factual defense may be simply a denial that the defendant did what is alleged. If he asserts that he was not even present at the occurrence, it is an "alibi" defense. Other factual defenses may make a virtual admission of the facts but allege the existence of additional circumstances that, under the applicable law, lessen the defendant's responsibility. In a typical automobile accident case, the defense may be that while the defendant was negligent, the plaintiff himself contributed to his own injury by also being negligent.
Special defenses in criminal cases may include the assertion that the defendant was insane at the time, that he acted in self-defense, that he was forced to act against his will, or that he comes within some particular exemption, as being duly licensed to carry a concealed weapon.
A defense may also consist of an attack on the legal sufficiency of the criminal charge or civil claim: for example, that the statute alleged to have been violated is unconstitutional (because it violates guaranteed rights or is too vague), that the law does not permit recovery of damages even if the alleged facts are true, or that the evidence produced fails to establish the charge or claim. In criminal cases, a defense tactic may be to try to suppress critical evidence on the grounds that the police used illegal methods to obtain it, or to rely on some other violation of due process.