“They arguably violate the Hippocratic Oath in having a doctor perform them”
The Hippocratic oath is something they do at medical school. It isn’t a law.
Easiest method. Offer the inmates 1+ month unlimited drug use of their choice (no meth) with their approval that at some time after 1 month they will get an OD at random. Most inmates on life without parole would take that deal. Throw in some women prisoners for comfort and you might get some without life/death penalties. Call it assisted suicide and the liberals will be all for it.
Why is it so complicated? Take a bullet in the head and give them an opportunity to donate their organs. Why the complication just to make the witnesse fell better?
I’m partial to Ol’ Sparkey.
5.56mm
Wikipedia on inert gas asphyxiation
There is a section regarding capital punishment
https://en.m.wikipedia.org/wiki/Inert_gas_asphyxiation