Yet despite convincing new evidence of the system's fallibility, neither Gov. George W. Bush nor Vice President Al Gore has defended his support of the death penalty in ways that confront the intellectual, legal and moral issues raised by state-sponsored killing. 

The foundation principles of a society in which citizens submit to the rule of law are that the guilty will be subject to proportional punishment and that the innocent will be vindicated through a fair and rigorous legal process. But neither principle can be said to govern how the American courts dispense death sentences. New research on error rates in capital cases and the successful use of DNA evidence to exonerate death row inmates in recent years reveal the system to be even more flawed than previously imagined. 

The execution of Gary Graham in Texas last night is a dramatic case in point. There is powerful evidence that he did not commit the murder for which the state put him to death. 

Mr. Graham, represented at trial by a court-appointed lawyer who failed to mount a meaningful defense, was convicted largely on the testimony of a single witness who said she saw him from 30 to 40 feet away through her car windshield. There was no physical evidence linking Mr. Graham to the crime. Tests showed that the gun he was carrying was not the murder weapon, and two other witnesses who were never called to testify at trial said they had seen the killer, and it was not Mr. Graham. 

Even for death penalty supporters, these facts should raise deep doubts about this conviction. But Mr. Graham is dead now, and the uncovering of further evidence that proves him innocent will not bring him back. 

Mr. Bush did nothing to stop the Graham execution, but instead defended his state's actions, telling reporters that "as far as I'm concerned there has not been one innocent person executed since I've been governor." Mr. Bush has now presided over 135 executions. In Illinois, Gov. George Ryan declared a moratorium on executions after 13 death row inmates were exonerated, as compared with the 12 who had been executed since Illinois reinstated capital punishment in 1977. It defies common sense to conclude that Texas, a state with a notoriously weak public-defender system, could conduct such a huge number of rapid executions without a single mistake. 

Mr. Gore has a more nuanced position, but one that is also deeply troubling. He was quoted this week by The Associated Press as saying that "if you are honest about the debate you have got to acknowledge there are always going to be some small number of errors." This chilling concession should rule out the use of capital punishment entirely. Any wrongful execution is constitutionally repugnant and erosive of the core values of justice in the United States. 

Mr. Gore does say that any state with a bad record of death penalty errors should declare a moratorium. But his statements about mistakes in the process seems to imply that there is some level of error that would be socially 
tolerable. Mr. Gore and Mr. Bush present themselves as leaders driven by moral principles. But by any moral standard, there can be no margin for error when the state takes human life.