What's all the fuss about over what drugs to use for executions?
It's not like we don't know how to euthanize humanely. We've been doing it for decades.
One of my first jobs in my teens was as a Vet Tech so I participated in numerous pet euthanasias.
Most recently, the cat that adopted me finally became so infirmed, that no amount of hospice care would relieve her suffering. Sad trip to the vets.
After the vet examined her and agreed it was time (past time, probably), a very good nurse/technician administered a single intravenous injection while I held her cradled in my arms like a baby (our usual way). She slipped off to sleep safely and peacefully. The vet came back a couple of minutes later and verified she was gone.
There's only one reason I can think of for our current state of affairs in criminal executions ...
... as it has always been, people are using religion ("People are not animals!") to justify torturing to death anyone who disagrees with them.