Under the law, citizens, including off-duty police, are allowed to use only that amount of force which is actually and reasonably necessary to thwart a threatened illegal act. The use of force in making an arrest is not only necessary in some cases, but may be provided for by statute. A person making a citizen's arrest would probably also be justified in using force to make that arrest. Force may also be used to detain a suspect or to prevent the destruction of evidence. Certain occasions may warrant the use of deadly force, which, is legal and proper, may be classified either as excusable or justifiable homicide. Any other unintentional killing that does not fit the criteria set out for excusable or justifiable homicide is a criminal act that may be called involuntary manslaughter, second degree murder, or even first degree murder, depending on the degree of recklessness involved. Deadly force, the use of which is limited by the Constitution, is justified only when the apparent peril is imminent. In some cases, a defendant may argue that his actions should be excused on grounds of duress or necessity.