I don’t even see why the electric chair needed to be invented. What’s wrong with hanging? If it’s done right it kills instantly, if not it leads to potentially-erotic asphyxiation, and it requires no equipment more expensive than rope and wood.
Maybe they should hang the person a little every day and then, SURPRISE! Cut them down before they die. Except one day not.
From the point of view of the victim, I don’t really think the randomness would be welcome. On the one hand, there’s no build-up to it so you indeed avoid the mounting anguish of the last few minutes inherent to current execution methods. But on the other hand, the fact that the room might just become a death trap next minute, every minute, would probably make people go stark raving crazy. Incertitude is way worse than grim certitude.
Answer’s in the question. Hanging somebody right requires skill, which can hardly be gained anywhere else - so trainee hangmen might botch a few… and auto-erotic or not a botched hanging sure doesn’t *look *pleasant.
Also, it involves the hangman’s will, which historically led to some very shady business (e.g. schemes where the hangman would hit the future hanged for money else he’d deliberately do it wrong, or deliberately did it wrong if they thought the criminal deserved extra punishment. Axemen did it too before the days of the guillotine.)
Yup, but then again, “First, do no harm”. Proper doctors should not be involved in killing people. Well, not deliberately anyway 
But you can use the argument that an illtrained guard can cause a botched execution, painful or botched in some other way. Having a properly trained medical person doing it ensures that it will be done properly, and in as painless a manner as possible.
Oh, you absolutely can. But again, the Hypocratic Oath doesn’t call for “First, try to minimize harm you are aware of”. And as a patient, I wouldn’t want my doctor to start pondering when and where he’s entitled to make the decision to kill people. “Never” is perfectly fine by me. For one thing there are painless execution methods that do not call for a doctor making this determination, for another the death penalty is a fucking abomination, period. So, yeah.
The Hippocratic Oath has traditionally been why doctors wouldn’t involve themselves in lethal injections. But if you separate events, then the doctor just properly renders them unconscious, and that’s all they’re doing, which they do normally anyway. And if they consider the longer sequence of events, then they’re just giving the condemned a less terrible way to face execution.
It’s a bit sophistic, but if you separate the first injection from the last by a couple hours, I imagine you could find a doctor or two willing to do it. “They’re gonna die anyway, at least (with my help) they’re unconscious for it”.
I am not getting into yet another death penalty is the evil discussion. The doctor isn’t making any sort of determination about who/when and die, the court has sentenced someone to die, the doctors job is to make it painless and efficient with as little trauma to the condemned as possible.