There's the death penalty in some U.S. states. However, performing executions by lethal injection has been difficult lately because of a rather absurd reason: lack of sodium thiopental, which is used in the process of killing the convict painlessly. Nobody seems to be willing to manufacture this drug, and thus it is now "effectively unobtainable" in the United States.
I consider it absurd because so far the human race has shown incredible ingenuity in the art killing other people. It's really quite amazing that a modern developed nation cannot find a good way to kill those it has decided to kill. At the same time, owners of dogs, cats and other pets shed tears as they perform the last service to the creature they love, and contract a veterinarian to put the animal to sleep forever.
But of course, what works with dogs will mostly work with people. According to CNN, the Oklahoma death row inmate John David Duty was executed with pentobarbital, drug often used to put down animals. His lawyers were protesting because the drug is "unproven in humans". Well, not any more. For once, we've had lots of animal testing. Would we need more human testing?
Myself, I'm for the death sentence for some crimes, but only with one approved execution method: lock the convict up in a prison until he or she dies.
The unpleasant fact about other ways of execution - however human and painless - is that they are too quick. It sometimes happens that a wrong man or woman is convicted. And once the execution is carried through, there's no way to undo it. But if the execution is performed by just keeping the person in prison, it is always possible to interrupt it if new evidence comes up.
Naturally, it may happen that the person dies in between the wrong conviction and its revocation. But when you consider that many death row inmates probably have a longer life expectancy in death row than outside - drug-related violence is a common reason for convictions, and incarceration reduces that risk; prison food is probably low cholesterol, low salt etc, in other words much healthier than what the convicts would otherwise be eating - this is a bearable risk. And remember, we have the same risk of miscarriages of justice with regular prison sentences as well. If you find a wrongful conviction, you can pay reparations, but you cannot give back time. And finally, the legal costs related to other types of execution seem to mount up so huge that the cost of a hundred years of prison meals is nothing.
The one question where I haven't quite made up my mind is whether people sentenced to death, and being executed for the next day or year or 100 years in prison, should be allowed to voluntarily choose a dose of a drug that gives them sleep. Right now I think not, both because it might be a too easy escape and because it might be a wrong escape.