(This op-ed was originally published in the Atlanta-Journal Constitution on January 2, 2009.)

Brian Nichols' life sentence without parole has provoked angry reactions from many people. They argue that, given the heinousness of his crimes, if anyone deserves the death penalty Nichols does.

But this argument reflects a fundamental misunderstanding of death penalty law. For over 30 years, the United States Supreme Court has consistently held that the decision to sentence a human being to death must be based not only on an assessment of the crime but also an assessment of the defendant's life history.A jury acts illegally if it sentences a defendant to death based solely on its assessment of the heinousness of his or her crime.

Three jurors in the Nichols case apparently understood this central tenet of death penalty law. Unfortunately, many jurors serving in capital cases do not. In fact, numerous empirical studies — including an exhaustive study by the Capital Jury Project which conducted almost 1,200 juror interviews from 353 capital trials in 14 states, including Georgia — have demonstrated that jurors often act contrary to the law when deciding that the defendant must die.

One of the biggest problems is that many jurors decide to impose a death sentence after hearing the facts of the crime but before the defendant has had an opportunity to present evidence of his life story, or what the law refers to as "mitigation" or "mitigating circumstances." The U.S. Constitution requires that jurors fully consider capital defendants' mitigation before deciding their punishment.

The studies also demonstrate that many jurors miscomprehend the definition of mitigation. "Mitigation" is a legal term.It refers to facts about the defendant's character, background or history, or the nature or circumstances of the offense which, in fairness and mercy, legally constitute a basis for a sentence of life imprisonment without the possibility of release.

It does not mean a legal defense or legal excuse for the crime such as duress or insanity at the time of the offense.Nor does it mean a lack of specific intent to kill or incompetency to stand trial.

However, many jurors do not consider a mitigating circumstance an adequate reason to impose a life sentence as opposed to a death sentence unless it either proves that the killing was not deliberate or furnishes a legal excuse for the killing such as insanity or duress.

Other serious problems revealed by the studies include:

• Many jurors misunderstand the legal standards governing their consideration of mitigating circumstances. They believe that mitigating circumstances must be proven beyond a reasonable doubt and that the jury must be unanimous in finding a mitigating factor.However, the law does not require that mitigating circumstances be proven beyond a reasonable doubt or that the jury be unanimous in finding them.
• Many jurors believe that the true sentencing responsibility rests elsewhere, including in the appellate courts.In fact, the law considers a jury's sentencing decision final, and trial judges, appellate courts and elected officials will almost never overrule it.
• Many jurors are under the misimpression that a capital defendant will be released from prison if given a life sentence, and they vote for the death penalty because the trial judge fails to correct that misimpression. The reality is that a sentence of life imprisonment without parole means that the defendant will die in prison of old age.

The U.S. death penalty system is a failed government program unworthy of a people that cherish fairness and justice. If we needed any further proof of this fact, the Troy Davis case seals the deal.

On September 23, 2008, Troy Davis came within two hours of being executed. He was at least temporarily saved when the United States Supreme Court granted a last-minute stay to give it time to decide whether to review his case. But Troy is not out of the woods. If the Supreme Court decides not to take his case, he will once again face execution.

Troy Davis has steadfastly maintained his innocence for all of the many years he has been imprisoned on Georgia's death row. An African-American, Davis was convicted of the murder of a white, off-duty Savannah Police Officer named Mark MacPhail in 1991. Not a shred of physical evidence links him to the crime. No murder weapon has been found. Nine non-police witnesses testified against him at trial, but all but two of these witnesses have either recanted their testimony or gave contradictory statements prior to Troy's trial. Some of the recanting witnesses now assert that they were coerced by police to say that Davis was the murderer. One of the witnesses who did not recant was seen acting suspiciously the night of Officer MacPhail's murder and has been heard boasting that he killed an off-duty police officer.

As extraordinary as it seems, despite the collapse of the case against Troy Davis, and despite the pleas on Troy's behalf by such leading figures of moral authority as Pope Benedict XVI, former president Jimmy Carter and Nobel Peace Prize-winner Desmond Tutu (PDF), the State of Georgia still wants to execute him.

This deeply troubling case illustrates four truths about our capital punishment system.

First, it is fraught with error. In the past 35 years, 130 innocent death row inmates have been exonerated and released after years on death row, and eight men have been executed even though there were serious questions about their guilt. In other words, the system can't reliably determine who is guilty, let alone who deserves the death penalty. And, despite popular myths, DNA is no panacea to the scourge of wrongful convictions and executions. It is available in only 10 percent of all murder cases.

That's Troy Davis' biggest problem. He cannot convince some death penalty supporters that he is innocent because there is no DNA evidence available to conclusively exclude him as the culprit. These supporters of capital punishment defend his conviction and death sentence by citing the flimsy evidence presented at his trial. But then they turn around and demand that Troy Davis prove his innocence with unassailable, irrefutable evidence.

That's not how our capital punishment system should work. When it comes to the death penalty, innocence should never have to be proven beyond a shadow of a doubt. We must not execute a human being if there is any legitimate chance that he is innocent.

Second, our judicial system can no longer monitor and control the use of capital punishment. Courts and legislators have made it so difficult for death-row inmates to challenge their convictions and death sentences that the system is unable to correct its own mistakes. It has become like an 18-wheeler barreling down a mountain, with no run-off lanes to stop it.

Third, the death penalty is infected by economic discrimination. It's a poor man's penalty. It is about poor people receiving death sentences because their lawyers were too overworked and underfunded to properly represent them.

Some politicians love to go around proclaiming their support for capital punishment but then they turn around and refuse to pay for a fair system. Capital defenders are given grossly inadequate time and resources to adequately defend their clients. We are seeing that again today with the funding crisis in Georgia's system of providing lawyers for poor people. Fourth, the death penalty discriminates on the basis of race. Study after study in state after state, including Georgia, has demonstrated that, everything else being equal, a defendant is about three to four times more likely to get a death sentence if he kills a white person than if he kills a person of color. And the combination most likely to get the death penalty is a black defendant convicted of killing a white victim.

As former Supreme Court Justice Harry Blackmun declared: “race continues to play a major role in determining who shall live and who shall die.”

In short, the Troy Davis case is a no brainer. The State of Georgia must not execute him. After all, as Justice Blackmun also once said, the execution of an innocent man comes perilously close to murder.