In his recent Supreme Court opinion upholding Kentucky's execution method, Chief Justice John Roberts says the state's lethal injection procedure passes constitutional muster because it does not pose "a substantial risk of serious harm." You might think serious harm would be hard to avoid with a procedure that's designed to take someone's life.

Roberts, of course, is not talking about the harm that inevitably occurs when someone dies; he is talking about the possibility of pain on the way to that final destination. This strange fastidiousness about making murderers as comfortable as possible when we kill them suggests that capital punishment in this country is ultimately doomed.

It's not doomed because it violates the Eighth Amendment's prohibition of "cruel and unusual punishments," contrary to what Justice John Paul Stevens now seems to think. As Justices Antonin Scalia and Clarence Thomas point out in their concurring opinions, a penalty explicitly envisioned by the Constitution (which refers to capital cases and says the government may not take someone's life without due process) can hardly violate the Constitution.

No, capital punishment is doomed because most Americans, including many who ostensibly support it, are not truly at ease with the idea of killing a man in cold blood. On balance, that is probably a good thing.

This discomfort with executions is reflected in what initially seems to be a needlessly complicated lethal injection process. In Kentucky, as in the vast majority of the 36 states with death penalties, condemned prisoners receive three different drugs: sodium thiopental, a barbiturate that would be fatal on its own in a large enough dose, to knock them out; pancuronium bromide to paralyze their muscles; and potassium chloride to stop their hearts.

The Eighth Amendment challenge to this procedure was based on the possibility that a prisoner might not get enough of the barbiturate to be fully unconscious. In that case, he would experience suffocation from the pancuronium bromide and severe pain from the potassium chloride without being able to communicate his suffering.

One solution to this potential problem, recommended by the two Kentucky murderers who brought the case, is to eliminate the pancuronium bromide so that the illusion of unconsciousness won't be mistaken for the real thing. In his opinion, Roberts cites two reasons why a state might nonetheless decide to continue using the paralytic agent.

"First," he writes, "it prevents involuntary physical movements during unconsciousness that may accompany the injection of potassium chloride. The Commonwealth has an interest in preserving the dignity of the procedure, especially where convulsions or seizures could be misperceived as signs of consciousness or distress. Second, pancuronium stops respiration, hastening death."

It's clear from these justifications that the state is trying to prevent discomfort not in the condemned prisoner (who, after all, is supposed to be unconscious) but in the people who witness the execution and, by extension, the general public. "Preserving the dignity of the procedure" is code for maintaining the illusion that a man the government executes is really just undergoing a medical procedure with a very high risk of fatal complications.

In the ebb and flow of American death penalty fashions, from hanging and firing squad through electrocution and the gas chamber to lethal injection, Roberts sees "an earnest desire to provide for a progressively more humane manner of death." I see an earnest desire to soothe an increasingly squeamish public.

As Fordham University law professor Deborah Denno has noted, the execution methods that are less unpleasant to watch are not necessarily less painful. "To me," she told The New York Times a few months ago, "the firing squad is the most humane and perceived to be the most brutal."

Around the same time, the Chinese government said it planned to switch from executions by gunshot to executions by lethal injection, which "is considered more humane," according to an official of the Supreme People's Court. Should that count as progress?