How about natural causes From old age in prison?
Old age in prison tends to mean you've been there for a while (unless you're one of those dangerous 80 year old murderers - watch out for them!). That's not a terribly pleasant experience - many would prefer to just get bumped off rather than spend forty years in prison with nothing but bars, three stone walls, three awful meals a day, and the strong possibly of getting ass-raped by one of the other inmates.
This whole thing has gotten me thinking - why, in the name of whatever deity you happen to believe in, do we bother talking about how "humane" these things are? No matter what option is selected for someone who has committed a serious crime, chances are it's going to be "inhumane." Toss a guy in prison and all that stuff listed above is going to happen to him and that's supposed to be more "humane" than just killing him?
I don't really understand all this talk about humane forms of execution, either. I mean, it's not like the guy whose getting killed is going to complain, right? And his relatives - well, what's their excuse? "His last moments shouldn't have been so painful." Think of it this way - he isn't in any pain now, right? "It was more painful for us to have to watch him suffer." Well then...don't watch! Executions should not be public affairs and they certainly shouldn't be attended by the family of whoever is getting killed. I mean, what do you say to your relatives in that position? "Come on, Johnny, time to go watch Daddy's life end! Don't forget to tie your shoes!" You want inhumane? Inhumane is allowing the people closest to the convict to watch his/her death. Let him see his family before you kill him, sure, but
don't let them watch. Can you say "psychological trauma"?