THIS NEWSPAPER OPPOSES the death penalty, as a matter of principle and of honest and decent law enforcement. Executions aren't only morally wrong – they don't deter crime. They cost the state millions of dollars. The people who die are almost always indigent, and most of them are people of color. And there's always the chilling and sometimes all-too-real chance that an innocent person will die.

So naturally we don't want to see Stanley "Tookie" Williams sent to die by lethal injection in the old San Quentin gas chamber.

But this is an unusual, and particularly compelling, case – and it ought to represent the turning point in the battle against state-sponsored executions.

Twenty years ago, Williams was a very bad man. He cofounded the Crips, the bloody and brutal Los Angeles street gang, and kept running the operation after he was sent to prison, where he was hardly a model of deportment. There are questions about the fairness of his trial, at which an all-white jury (blacks were perhaps illegally excluded) convicted him on the basis of what a federal court called "the testimony of witnesses with less-than-clean backgrounds and incentives to lie in order to obtain leniency from the state." Still, Williams would be the first to admit that his entire lifestyle was in effect one long violent crime.

But Williams changed. The poorly educated street kid read voraciously, came to terms with his ugly past, and decided to devote himself to keeping others out of the gang life. His books aimed at kids have been immensely effective; he's almost certainly saved thousands of lives in the past few years, and he's been nominated for a Nobel Peace Prize.

The Williams case goes to the heart of one of the biggest flaws with the death penalty: It assumes people can't change. If Williams had been executed 10 years ago, he might never have had the chance to become a leader in the antigang movement. And Gov. Arnold Schwarzenegger's decision on his clemency petition could be a decisive moment: If the Republican governor is willing to say it's wrong to kill Tookie Williams, it will at least open the door to further discussion about capital punishment.

The tide is turning: While a majority of Americans still supports the death penalty, the number is dropping – and eventually, the United States will join the rest of the civilized world in banning executions. Schwarzenegger should get out in front of that movement and save Williams from death row.