Chance of decapitation exists in hangings

LONDON -- Judicial hangings are designed to break the neck and choke a person to death as efficiently as possible, but decapitations can occur if the prisoner falls more than the prescribed distance.

The condemned person is typically dropped a distance greater than their height through a trapdoor. At that point, the rope becomes rigid, and the force of the noose should break the victim's neck, causing immediate paralysis and unconsciousness.

The procedure snaps the upper cervical spine, generally killing the victim by asphyxiation.

Though no one knows how long it takes a person to die from hanging, specialists say it is probably anywhere from a few seconds to a couple of minutes.

In judicial hangings, as opposed to suicides, there is significant damage to the spinal cord. If the victim falls more than the required distance, the person may even pick up enough speed that the noose itself causes decapitation. In rare cases, intense fear can cause the victim to die of cardiac arrest.

"The fracture obstructs their breathing, and they are left gasping for breath," said Harold Hillman, a specialist in executions who teaches at the University of Surrey.

Even when the neck is broken, Hillman said, there is still blood containing oxygen in the brain. The brain can still function at some level until that oxygen is used up.

The last major advance in the technology of hangings came in the 19th century, when tables were devised to calculate both the length of rope needed to kill, and the distance of the necessary drop.

According to these "drop tables," the heavier the prisoner, the shorter the distance needed to produce sufficient force to break his neck. Still, the tables are only a rough guide, particularly if the victim has a thin neck.