I am not strongly against the death penalty on principle or on moral grounds — assuming, of course, that it could somehow be narrowly and efficiently restricted to a very few egregiously deserving and certainly guilty criminals.

I don’t even find it particularly appalling (or cruel and unusual) punishment that a killer may have some few minutes of physical discomfort before expiring during a clumsily administered execution. My experience as a doctor teaches that dying is never that much fun, and I don’t see why a heinous criminal should expect a completely free terminal ride when this is not guaranteed to any of the rest of us.

But I do have a very strong objection to the death penalty based purely on practical economic grounds. Killing criminals, whether they deserve it or not, simply costs much more than our society can afford and provides far too little value in return.

Recently, I have appeared as an expert witness in two death penalty cases. Both trials dragged on for many months, produced thousands of pages of documentation, and engaged hundreds of witnesses — including a a platoon of experts arguing for each side.

There seemed to be a limitless budget with no attention to time or money. The stakes are so high in death penalty cases that every procedural nicety must be given its fullest possible due. Judges are extremely concerned about being reversed on a technicality by the appeals courts. This would be embarrassing to them and require a lengthy and expensive retrial. The safest way for a judge to achieve an appeal proof verdict is always to allow the defense the greatest possible leeway. This encourages defense lawyers to pose every possible objection and to weave every conceivable mitigating theory (however outlandish) hoping that, with enough stuff out there, something may stick with the jury or later with the courts of appeal. The fact that defense lawyers are on the clock (getting hefty hourly fees, usually supported by tax dollars) also provides them with a strong financial incentive to drag things out as long as possible.

Our adversarial legal process encourages an unenlightened and dispiriting dueling of expert witnesses. Their opinions are usually tailored to exaggerate the case for one side or the other — rather than seeking a truth that usually lies somewhere in between. Often enough, the expert seems to be little little more than a pliable hired gun.

And what is society’s reward for all this effort and expense? Precious little. In many states and in federal cases, the death penalty has become purely symbolic. Though offenders are sometimes sentenced to death, they usually wind up never getting executed; instead they live for decades in expensive death row cells. And in the states committed to actually following through on the death penalty, there is no evidence that executions have any more deterrent value than life without parole.

The price tag for the death penalty can reach tens of millions of dollars in any given case. Since budgets are always ultimately a zero-sum game, wouldn’t justice be better served and money better spent doing things that might actually reduce crime?

Increasingly, the death penalty has become an anomaly and an embarrassment. Already, 140 countries have eliminated it and the biggest sponsors are China, Iran and us. We are also in the bad company of an assortment of the more dubious Middle Eastern, African and Asian countries.

Only a few and weak arguments can be raised to support the death penalty — that it provides society with an opportunity to inflict just retribution, has an impact on deterrence, promotes a sense of closure for survivors, and is a bargaining chip to encourage criminals to confess and cop a plea.

Even if you buy into some or all of this, the exorbitant financial cost of the death penalty makes it unsupportable as public policy. And you also have to factor in the haunting possibility that the state may sometimes kill an innocent man.

Allen Frances is a psychiatrist and professor emeritus, Duke University.  He blogs at the Huffington Post.