There is nothing kind or gentle about a hanging. It is a process scientifically designed to break the neck and choke a person to death as efficiently as possible.
In the recent Iraqi executions, former president Saddam Hussein and two of his accomplices, his half brother and the former head of Iraq's Revolutionary Court, were hanged from a gallows.
In such judicial hangings, the victims are typically dropped a distance greater than their height through a trapdoor. At this point, the rope becomes rigid, and the force of the noose should break the victim's neck, causing immediate paralysis and unconsciousness.
The procedure causes a classic "hangman's fracture" — a break between the head and the neck, effectively snapping the upper cervical spine. In most cases, the victim dies of asphyxiation.
Though nobody really knows how long it takes a person to die from hanging, experts 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 victims fall more than the prescribed distance, they may even pick up enough speed that the noose itself decapitates them, as happened Monday to the former Iraqi dictator's half brother Barzan Ibrahim. In rare cases, intense fear can cause the victim to die of cardiac arrest.
"Hanging is a very cruel way of killing people," said Harold Hillman, an expert in executions who teaches at the University of Surrey. "The fracture obstructs their breathing, and they are left gasping for breath."
Even when the neck is broken, Hillman says, there is still blood containing oxygen in the brain. The brain can still function at some level until that oxygen is used up.
In praxes, this means that facial movements can still occur even after the head has been severed from the body.
The head of the Marie Antoinette, the guillotined French queen, famously smiled after being chopped off for precisely this reason, Hillman says. "Until there is no oxygen left, you can have involuntary movements in the head."
Criminals have been hanged since the Persian Empire first adopted the practice 2,500 years ago. The last major advance in the technology of hangings was made 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 so-called "drop tables," the heavier the prisoner, the shorter the distance needed to produce sufficient force to break his neck.
Still, these drop tables are only a rough guide, cautions Geoffrey Abbott, author of "Execution: The Guillotine, the Pendulum, the Thousand Cuts, the Spanish Donkey, and 66 Other Ways of Putting Someone to Death."
"A person could weigh an amount that required a length of 8 feet, but because his neck is particularly scrawny, his head might come off," Abbott said.
Iraqi officials said that the gallows were built in accordance with international standards, but human rights officials disputed that claim.
"Under no circumstances can an execution be in accordance with human rights standards," said Param-Preet Singh, counsel for the international justice program at Human Rights Watch.