The man family members say has been gentle, withdrawn, socially inept and supremely gullible since he was a child had no record of violence until 1969, when he was 26 and living in Missouri. By his own admission, he then choked, stabbed and drowned a woman he had just met. No one, including Beardslee, ever came up with a motive for the murder.

After seven years in prison and four mostly uneventful years on parole, during which he moved to Redwood City, Beardslee killed two more women in April 1981. He shot one and slit the other's throat. The apparent motive was revenge -- not by Beardslee but by drug-dealing associates of the teenager he had taken into his home to help her recover from an overdose. This time, the sentence was death.

After two more decades of exemplary prison behavior and unsuccessful appeals by Beardslee, his lawyers say new psychiatric tests have finally produced an explanation for his personality and actions: lifelong brain damage, compounded by a crushing head injury caused by a tree that fell on him when he was 21.

San Mateo County prosecutor Martin Murray derides that claim and says Beardslee, whose IQ is above the national average, is simply "ruthless and cunning.''

Both sides have some evidence for their conflicting portrayals. If Beardslee is executed as scheduled at San Quentin State Prison, he will go to his death as an enigma.

Donald Jay Beardslee was born in St. Louis on May 13, 1943, the oldest of three children. The portrait that emerges from his youth -- sketched by lawyers looking for evidence to save his life -- is that of a misfit.

"His communication was weird, he could not express emotion, he said socially awkward things, and he was forever naive,'' his sister, Carol Miller, said in a declaration that was part of the clemency request his attorneys submitted to Gov. Arnold Schwarzenegger. "All of the qualities that made him an oddball remained through the years as did his childhood vulnerabilities. He seemed to stay stuck at age 13 or 14.''

A cousin, Lynne Stephenson, said in another declaration that "the other kids noticed there was something 'off' about Don and teased him unmercifully. Don just took it. ... He would just become sad and quiet.'' She said he had no friends of his own, suffered from facial tics -- of which he seemed unaware -- and was eager to please and "easily duped and taken advantage of.''

Karen Kelly, who was married to Beardslee from 1966 to 1968, said he "had a hard time understanding other people, and other people had a hard time understanding him, mostly because he could not explain himself.'' He was passive, dependent, vulnerable and the last person she would expect to commit murder, she said.

Unlike the typical impoverished death row inmate, Beardslee grew up in a middle-class family. But his lawyers said he was traumatized as a youth, particularly by his father's death from cancer shortly before Beardslee's 11th birthday. At 15, he was sent by his mother to a military academy, where he was hazed relentlessly for three years, relatives said.

He enlisted in the Air Force at 19, spent four years as an aircraft mechanic and had his first serious run-in with the law when he was caught with another airman trying to steal a vehicle. While serving his sentence in 1965 on a work farm in Minnesota, he was hit in the head by a falling tree, which fractured his skull and put him in a coma for days.

In December 1969, Beardslee met Laura Griffin, 54, at a St. Louis-area bar, where they drank and danced for a half-hour and then went to her apartment. Two days later, police found her nude body in her bathtub. After talking with his minister and a lawyer, Beardslee went to the police and confessed. A psychiatrist and a social worker who interviewed him in prison quoted him as saying he had no reason to kill her and must have been addled by alcohol.

Beardslee pleaded guilty to second-degree murder and served seven years of an 18-year sentence before being paroled to California, where his mother lived. Several therapists in prison diagnosed him as schizophrenic, and one referred to possible brain damage; Beardslee sought counseling, but records indicate little was available.

He settled in Redwood City, got a job as a machine operator with Hewlett- Packard and stayed out of trouble until 1981. Then one day he saw Rickie Soria hitchhiking on El Camino Real and gave her a ride.

Soria was a street-tough 18-year-old who financed her drug habit by selling narcotics and sex, according to records provided by Beardslee's lawyers. Through her, Beardslee met her friends Stacey Benjamin, Ed Geddling and his wife, Patty, and Frank Rutherford, a drug dealer with a violent reputation.

When Soria was given a near-fatal overdose of drugs by Rutherford and another man in March 1981, she phoned Beardslee, who took her to an emergency room, then brought her home and nursed her back to health, she said in a recent statement from prison.

Evidence about the events that led to the murders is conflicting. There was testimony that another friend of Soria's, Bill Forrester, was angry at Benjamin and possibly Patty Geddling for cheating him in a drug deal and that Ed Geddling had found his wife in bed with Benjamin.

One witness said Ed Geddling brought Rutherford a shotgun and asked him for help in taking revenge on both women. How much Beardslee knew about the plans in advance is still in dispute.

On April 23, 1981, Soria invited Benjamin, 19, and Patty Geddling, 23, to Beardslee's apartment for a purported drug sale. When they arrived, Rutherford and Forrester were there.

Rutherford shot Patty Geddling in the shoulder and both women were tied up. Winking at Beardslee, he said Geddling would be taken to the hospital.

Forrester, Beardslee and Soria then drove her to a spot near Half Moon Bay, where -- according to prosecution testimony -- Forrester shot Geddling twice with the shotgun, then handed it to Beardslee, who reloaded and shot her twice more. They left her body in a ditch.

Rutherford then summoned Beardslee and Soria to his girlfriend's apartment, where Benjamin was still tied up. The three drove her to Lake County, where Rutherford tried to strangle her with a wire. According to trial testimony, Benjamin looked pleadingly at Beardslee, who punched her in the head, then tried to help Rutherford strangle her. Beardslee then got a knife from Rutherford and slit her throat.

Beardslee, whose phone number was found on a piece of paper near Geddling's body, was contacted by a detective, confessed his role, led police to Benjamin's body, named his cohorts and testified against them without any promise of leniency.

Rutherford was convicted of Benjamin's murder and sentenced to life. He died in prison two years ago. Soria pleaded guilty to second-degree murder and is still behind bars. Forrester, who denied shooting Patty Geddling, was acquitted, and charges against Ed Geddling were dropped.

Only Beardslee was sentenced to death in March 1984 for Patty Geddling's murder. He was the only participant in both killings and the only one with a murder on his record.

Throughout his trial and appeals, Beardslee's lawyers have portrayed him as a dupe in crimes orchestrated by others, chiefly Rutherford. Soria, in her recent statement from prison, said that after Rutherford first fired the shotgun in the apartment, Beardslee "became unnaturally quiet and robotlike'' and "just did what he was told.''

But prosecutors argued that Beardslee had a motive: Once the first shot was fired, he knew he was violating his parole and would be sent back to prison unless he got rid of the witnesses.

Rutherford was not present when Patty Geddling was killed, and Beardslee, in light of his record, "needs no encouragement from others to kill women,'' Murray said in a filing opposing the clemency request that went before the state Board of Prison Terms on Friday. The governor is still considering the request.

Beardslee's mental health was an issue from the start -- one juror said it was the chief concern of jurors who initially voted 10-2 to spare his life -- but it was only in the last month that his lawyers produced a diagnosis from a neuropsychologist, Ruben Gur of the University of Pennsylvania, of severe brain damage.

Gur said Beardslee was prone to confusion and paranoia during unfamiliar events and exhibited a "constricted emotional range'' that might be misinterpreted as aloofness or callousness. His lawyers say the diagnosis also explains why Beardslee has done well in highly structured settings, such as the Air Force and prison. While it's too late for courts to consider the evidence, the lawyers hope it will move the governor to mercy.

Murray, who represents the prosecutor's office, isn't buying it. Beardslee has been examined by legions of analysts who never detected any such thing, he said, and also has performed intricate tasks as a machinist and taken college courses, both inside and outside prison, with no sign of mental deficiencies.

"While psychiatrists, lawyers and judges carefully scrutinized every detail of this case," Murray said, "the families of his victims have patiently awaited justice for over two decades.''