When it comes to execution I think any Vet could do the job with no trouble, they routinely put down everything from cats to horses with no pain or strain.
That said, while I have a personal "better dead" list, I have no intention of doing anything about it. Society in general and our "Justice" system does a poor enough job finding the truth that I don't think we can execute people with any certainty of justice. It would be cheaper to do the life without parole route, and when we screw up we can say "sorry" and pay damages. It costs one to two million dollars per execution and I don't think that includes the jail time which runs 10-25 years. That isn't going to change any time soon and we have better things to spin our wheels on. We need prisons just for the life without parole crowd since they have nothing to lose. I'd rather be executed than serve life, but that's just me.
I don't think there is any doubt about the guilt of the latest cop killer, but there is a whole continuum from totally certain to iffy and our system across many states can't be trusted to make the distinctions any more than they can manage the VA or health care.