I have had some input to a different state's exploration of this approach.
The underlying problem is that they're trying to get around the pharmaceutical companies' block on sales of lethal injection drugs to state prison pharmacy inventories. So lawyers for both sides are preparing lawsuits either for or against the death penalty in several states. I've been asked some questions by some of those folks, and as a consequence I've done some medical research into the question.
In my opinion, execution by firing squad is the second-most-humane method in existence, after lethal injection. Five or six rifle bullets to the central chest/heart/mediastinum will effectively kill the recipient very quickly, with very little or no pain.
Death by hanging, electrocution, and poison gas can take a very long time in some cases. There are plenty of documented cases of failed executions involving all of these methods, and the prolonged agony of the condemned men and women cannot be dismissed lightly. Death by decapitation via guillotine is quick and certain, but the likelihood that the condemned suffers excruciating pain for several seconds before the brain shuts off from blood loss is high; and it's damn messy, much messier than shooting someone in the chest.
So if we're going to allow the State to kill criminals, firing squads are likely to become the standard method... unless the liberal executives who run the pharmaceutical companies back off from their intransigence.
