Here's the thing. Intentionally inflicting pain, be it physical or emotional, is cruel. Society has no business exercising the majesty of control over life and death in a cruel manner.
Lethal injection was, among other things, supposed to eliminate the possibility of the "horrors" of other methods gone wrong. But then the weenies got into it and insisted it be not only "painless" but something the condemned would not be aware of at the final moment - the supposed knowlege and physical experiences between when the trap dropped and they came to the end of the rope, or between when the rifle fired and the bullet struck, etc. All of which has always seemed to me to be taking away one of the primary purposes of a state execution - that the condemned be aware, in the literal sense as opposed to some philosophical way, that the state was taking their life.
So, since hanging and beheading and electrocution and cyanide gas and the like are all now in "disfavor", how do we go about ending the life of the condemned in a quick, efficient, method that is not cruel and also does not depend on the emotional whims of some drug manufacturer? Without singling out any specific ideology since several of them used it, I suggest an injection directly into the heart of any of a number of commonly available chemicals. To be crude - but not cruel - about it, use something you can get as easily as by going to the local gas station.
A state execution is not a medical procedure. Medical personnel are not needed until it is time to confirm the condemned is well and truely dead.
stay safe.