I may be wrong on this but I believe they draw names like court duty. When they have 5 citizens willing to do their duty they step up to rifles which are pre aimed and pull the triggers. Only one rifle has a live round. The rest are blanks. No one knows who fired the kill shot. I believe this is how Utah does it.
I heard the opposite. Only one rifle has a blank. That makes more sense. With only one live round, the prisoner might only be wounded if the shooter was having an off day.
There’s quite a difference in recoil between firing a live round and firing a black.