Elizabeth Weil in the New York Times Magazine:
Lethal injection is the most recent attempt to find a way to transport condemned inmates from life to death in a manner that does not offend our civilized sensibilities. Over the past 100 years, states have chosen from, and discarded, as many as five execution techniques. As a dominant method, the noose has been replaced by the electric chair and the electric chair by lethal injection. Some states also cycled through the firing squad and lethal gas (all five methods still remain options in one state or another). Each change in technique was based on the notion that the new method would be better — more dignified, less gruesome — and in some ways each has been. Nooses, if the drop is too short, can leave bodies twitching for up to 45 minutes, and if the drop is too long, as it was for Saddam Hussein’s half brother, the condemned can fall with so much force that his head is ripped off. Firing squads are considered too violent. Lethal gas takes too long; the 1992 lethal-gas execution of Donald Harding in Arizona was so long — 11 minutes — and so grotesque that the attorney general threw up and the warden threatened to quit if he were required to execute someone by gas again. The electric chair often results in horrible odors and burns; in Florida, in the 1990s, at least two inmates heads’ caught fire, and the chair routinely left the condemned’s body so thoroughly cooked that officials had to let the corpse cool before it could be removed.
More here.