Couldn't they just use an electronic guillotine and have it set off by the public watching the beheading. Say the public watching all hold a hand held controller with YES and NO buttons only. And if just one person in the crowd presses YES, the guillotine comes down and beheads the person. No one would know exactly who set it off. Or the government could actually have one controller rigged to make the guillotine come down regardless of what they press. Or they could have both buttons be rigged to set off the guillotine.