So this isn't a debate for or against capitol punishment, but if we're going to do it, what's the best way?
Electrocution, gas chamber, and lethal injection are all criticized as either too barbaric as it is sometimes painful and takes guys hours to die, too unreliable if performed incorrectly, too expensive, or all three.
Mississippi is thinking of bringing back the firing squad, like Utah has used up until recently as 2010.
Basically you give 5 proven marksmen rifles, four with live rounds and one with a blank. (The one blank provides what's known as the "diffusion of responsibility" and let's each marksman reasonably believe that he might not have fired the killing shot.)
You give the condemned person, restrained in a chair so he can't move, a hood and white shawl featuring a bright red heart over where his heart is as a high-visibility target. Then the shooters fire on command from 25 feet, or "can't miss", range. Death is immediate but it takes the doctor 30 seconds to walk in and confirm it so legally death takes 30 seconds.
There are insane citizens that support public hangings or the guillotine, and both do result in reliable, instantaneous death, but I doubt we'll be seeing those spectator events anywhere except Game of Thrones, which leaves us with the firing squad as the most humane, reliable, and cheap way to dispatch a dude who needs dispatching. IMHO.