Decapitation is the total separation of the head from the body. This injury is fatal to humans and all vertebrate animals, since it deprives the brain of oxygenated blood by way of severing the jugular vein and common carotid artery, while all other organs are deprived of the involuntary functions that are needed for the body to function. The term beheading refers to the act of deliberately decapitating a person, either as a means of murder or as an execution; it may be performed with an axe, sword, or knife, or by mechanical means such as a guillotine. An executioner who carries out executions by beheading is sometimes called a headsman. Accidental decapitation can be the result of an explosion, a car or industrial accident, improperly administered execution by hanging or other violent injury. The national laws of Saudi Arabia and Yemen permit beheading. Under Sharia, which exclusively applies to Muslims, beheading is also a legal punishment in Zamfara State, Nigeria. Cases of decapitation by suicidal hanging, suicide by train decapitation and by guillotine have been documented.