I always have to wonder who got a kick back buying these overly complicated expensive execution systems. The automated injection systems and drugs that make lawsuits easy for the civil rights lawyers.
A simple gas chamber from the 1930s modified to use a cheap industrial gas like nitrogen would be very simple to use and painless.
All that is need to put a prisoner to death is to replace the air in the chamber with nitrogen and the prisoner would be in respiratory arrest in less than a minute and brain dead in less than 10.
Because the pain associated with asphyxiation is caused by excess carbon-dioxide in the blood the asphyxiation caused by the lack of oxygen in the air does not cause pain.
Prisoner executed in this way will not experience pain.
I am of the opinion that executions need not be painless.
What the Constitution requires is that the execution be performed in a manner that does not cause pain for the sake of causing pain.
Just like going to the dentist using NO2. Just adjust the nitrogen slowly, he’ll get a nice buzz before checking out