Human medical experimentation on prisoners is cruel and unusual in and of itself. However well you personally think execution by nitrogen would go (and I doubt you’d volunteer), people on death row have a right to know we’re not trying novel execution methods on them. Maybe if what we’re doing doesn’t actually benefit anyone more than prison would and is considered so barbaric that European manufacturers won’t supply us with the drugs we need to do it, we should stop.
The mania for execution led Arizona to refurbish its gas chamber and reverse-engineer a Zyklon B equivalent.* That’s not the kind of country I want to live in. How about you?