YOU MAY BE the last person in the world to stand outside San Quentin Prison on a foggy night with a candle in your hand to protest an execution. You may be frustrated about all the appeals that cost so much money and delay justice. You may even think the death penalty should be carried ent to crime.

You still should be worried about the August 5 execution of Thomas Thompson. If anything, death-penalty proponents should be especially anxious about this case.

Nothing threatens California's return to capital punishment -- which has reduced Death Row's population by four in the past five years -- as much as the possibility of a mistake.

It took a pretty dedicated abolitionist to plea for mercy before the state in 1992 gassed Robert Alton Harris, a career thug who mocked the mercy pleas of two 16- year-old boys before he shot them and ate their hamburgers. The next three executed murderers -- David Mason, ``Freeway Killer'' William Bonin, Keith Williams -- were equally villainous. They all went to their deaths leaving multiple victims, little if any remorse and sloppy trails of evidence pointing to their obvious guilt. What little debate remained before their executions focused on issues such as whether childhood abuse somehow lessened their culpability. Not exactly a sympathetic argument to a public fed up with excuses for violence.

The Thompson case is not so clear cut.

Thompson, now 42, was sentenced to death for the 1981 rape and murder of Ginger Fleischli. His accomplice, David Leitch, was convicted three years later of a lesser charge -- second-degree murder -- and sentenced to 15 years to life in prison. He is now eligible for parole.

Fleischli, 20, was stabbed five times in the head with a single-edged knife inside the Laguna Beach apartment shared by the two men. Her body was found at an Irvine nursery, wrapped in a sleeping bag and pink blanket, and covered with dirt.

To this day, there is a legitimate question about which man did exactly what in the early-morning hours of Sept. 12, 1981. And those distinctions are critical in establishing why Thompson -- and not Leitch -- faces lethal injection on August 5. There was an unsettling aura of convenience about the prosecution of those cases. When they initially wanted to try the two men together, prosecutors found a jailhouse informant who claimed Thompson confessed to joining Leitch in the killing.

Later, as Thompson was tried separately, two jailhouse snitches with questionable track records of reliability testified that the defendant confessed to raping and killing the victim by himself. Curiously, both witnesses said Thompson described stabbing her in the head and upper torso and putting her in a shallow grave. This was the way the crime was described in early press reports. But Fleischli was neither stabbed in the torso nor buried below ground level.

Prosecutors never produced a murder weapon or physical evidence to link Thompson to the crime. The same deputy district attorney offered amazingly contradictory theories in the two trials -- in the Thompson trial, it was characterized as a one-man rampage; in the second trial, Leitch was described as the instigator of a two-man plot. Seven seasoned state prosecutors, including the state's death-penalty author, have asked the U.S. Supreme Court to intervene. ``Should evidence later be uncovered demonstrating Thompson's innocence or lesser culpability,'' they wrote, ``it will be tragically too late for justice to prevail.''

Are you still ready to execute this man?

California law specifies that the death penalty applies only in murders accompanied by ``special circumstances'' determined by the Legislature or the electorate -- a growing list that includes multiple victims, drive-by shootings, rape, robbery or kidnapping.

This is where the case for Thompson's execution gets especially murky.

The ``special circumstance'' of rape elevated Thompson's conviction to a capital crime. Yet Leitch had told his lawyer in 1982 that he had walked in on Thompson and Fleischli while they were having consensual sex the night of the killing -- a point he reiterated at a 1995 parole hearing.

The rape allegation is weakened further by a coroner's finding that, aside from the stab wounds, there was ``remarkably little trauma'' on the victim's body.

Jurors never heard any of that evidence. Neither point proves she was not raped, but, combined, they raise real doubts about the sexual-assault allegation. And if she was not raped, this was not a

capital crime. U.S. District Judge Richard Gadbois Jr., a Reagan appointee, two years ago reviewed 7,000 pages of transcripts and struck down the rape conviction. Two of the jurors from Thompson's trial, after learning about some of the new evidence considered by Gadbois, issued a

statement declaring they now ``have some doubt'' about their verdict.

However, a U.S. Court of Appeals overturned his ruling.

The death march proceeds.

So who killed Ginger Fleischli? Thompson points the finger at Leitch, who is now locked up at the California Men's Colony at San Luis Obispo.

Leitch has admitted only in helping to dispose of the body.

``What Tom hopes is sooner or later . . . he can clear his name and will be free,'' said Quin Denvir, his appellate lawyer of 13 years. ``He has remarkable faith in the system. He still believes this can't happen in America.''

There is not nearly enough evidence now to even think about freeing Thompson. It is hard to look at the case without getting the feeling that his actions that night -- whether they included a vicious stabbing or merely helping conceal a body -- earned him a place in prison.

But he should not be put to death with so many questions still lingering.

The state attorney general's office argues that the judiciary process has run its course; that it is time for Thompson to die. However, California law, reflecting the gravity of capital cases, has an additional fail-safe element built into the system. Governor Wilson should grant clemency to Thompson, which would keep him in prison without the possibility of parole. Such an action would recognize the doubts of a judge, seven prosecutors and two jurors, and assert the state's respect for the sanctity of life. A clemency order would help uphold the very integrity of the death penalty.

The state cannot afford a mistake here.