Spotted in the LA Daily News and reported on the WELL:

Decapitation Mars Hanging in Baghdad

Later: That headline of course refers to the execution of Saddam Hussein’s half brother. Now I have learned on the WELL that this was a matter of using too long a rope. Apparently the length of rope needed to break the neck cleanly is related to the condemned person’s weight. If the rope is too long, the weight of the person falling will cause decapitation; if too short, the neck may not be broken and the person will die slowly and unpleasantly from strangulation.

Here is a link to the Official Table of Drops created by Britain’s Royal Navy. And here is another to more information than I really needed to know about the physics of execution by hanging.