I will bow to your greater experience in this area.
I’m still confused about why this seems to be such a difficulty, though.
We have the ability to routinely induce deep unconciousness through anesthesia, right?
So why not anesthetize someone, then switch the gas being fed through their mask to pure nitrogen? They’re unconcious, so they don’t feel anything, but death occurs within a few minutes from anoxia.
I’m even told that just feeding nitrogen to someone will quickly knock them unconcious, then kill them. Haven’t tried it personally. :)
Why do we make this so complicated?
As you say, bullet in the head or the guillotine are quick and presumably painless. Or if there is pain, it sure doesn’t last long. Although each method is a lot messier than a needle.
see my comment 92.