Joan Barthel has an interest in murder and an eye for injustice. Her previous book, "A Death in Canaan," was the story of Peter Reilly, a Connecticut youth who was unjustly accused of murdering his mother; the book played an important role in the process that eventually led to his release. In "A Death in California" the injustice is similar, involving as it does a person unfairly accused -- but it is also considerably more complicated.

The murder took place in February 1973, at a ranch outside Los Angeles. The victim was Bill Ashlock, an advertising man in his early forties. Sometime after he was murdered, his fiance', Hope Masters, who had gone to bed early, was attacked in the dark and raped at least twice. As she became familiar with her attacker, she realized that he was "Taylor Wright," who had visited them the previous day to take pictures of Bill for an article he ostensibly was writing for the Los Angeles Times about the city's most eligible bachelors.

Hope Masters, who was 31, was a daughter of Los Angeles society; her stepfather was a law partner of William French Smith and gave her mother a $3,000-a-month allowance. Hope was petite, beautiful and troubled; she had been married twice, had three children, and lived in near-poverty, notwithstanding her family's wealth. She was naive and impressionable; and after the events of the night at the ranch, she was scared within an inch of her life.

She was also oddly infatuated with "Taylor Wright," whom she realized was not merely her own rapist but also Bill Ashlock's murderer. After clumsily raping her, he suddenly changed tone and began speaking to her in affectionate, even devoted, tones. He told her an elaborate story about a "contract" being put out by her husband on her life, and the lives of two of her children. He told her that he regretted Ashlock's murder (the first of the injustices in the case, Ashlock being in effect an innocent bystander), and that he would not make her his second victim so long as she conspired with him in a cover story.

Which she did, with the not-surprising consequence that she herself was accused of the crime: injustice No. 2. Her stepfather hired high-powered criminal lawyers, who in turn hired a high-powered private eye; but so long as she refused to tell anyone what actually happened, the chances of getting her off seemed slender at best.

But gradually she began to talk -- first to her mother, then to her lawyers. At the same time, "Taylor Wright" flitted around the edges of the case in a beguiling, infuriating way -- calling Hope, sending her tape cassettes, calling her parents, calling her lawyers. No one could find him, yet he refused to vanish.

One clue led to another, and at last the story of "Taylor Wright" began to emerge. His real name was G. Daniel Walker, and he was an escapee from an Illinois prison. He had shot an Illinois state trooper; the man's life had been saved only by the bullet's freakishly harmless passage through his skull. A fellow policeman, Robert Swalwell, had vowed to recapture his friend's assailant and had made the case a personal mission.

G. Daniel Walker, as his personality gradually evolves in Barthel's skillful portrait, is an uncommonly interesting fellow: a man of unusual intelligence, good looks, sexual magnetism -- and a seemingly insatiable appetite for bloody thrills. In Swalwell's description: "He just needs that little extra something to make life interesting. He uses people. He could shoot you, then sit down and have lunch right beside your body and it wouldn't faze him. He's just a bad seed. An amoral human being."

Eventually Walker was caught -- and placed on trial along with Hope Masters for the murder of Bill Ashlock. The jury, it seems, was to decide which, if either, of them did it. But the judge and the lawyers made the decision for them, exonerating Hope in return for her testimony against Walker. She gave it, and he was convicted; but she gave it reluctantly and without enthusiasm.

To say that she had fallen in love with Walker would be excessive, but she had fallen under his spell. She kept remembering that he had not murdered her, when he had had every opportunity to; that he had been gentle with her after raping her; that he had drawn up a cover story that was designed to clear both of them; and that he had not completely fled the scene, leaving her to face the murder charges by herself. She said: "Walker and I have a very deep, odd thing together."

The final injustice is that Hope Masters, though innocent and a victim, has been found guilty -- "guilty of something," she told Barthel -- by society. The wealthy, complacent world in which she grew up now rejects her; the moral judgments have been made, and she has been found lacking. She has matured enough to be able to live with this, but she understandably -- and properly -- finds it outrageous.

So, obviously, does Joan Barthel; but she keeps her outrage under control. She lets the facts of the story speak for themselves. Though she is a practitioner of the "new" journalism, she employs it responsibly; she names her sources, and she permits herself to express the thoughts and feelings only of those people who have talked with her.

The one person with whom she evidently did not talk was G. Daniel Walker, so we are left with some basic mysteries at the core of the case. Why did he choose Bill Ashlock and Hope Masters as his victims? What singled them out from the crowd? Why did he play cat-and-mouse with the cops, eventually allowing himself to be recaptured?

Through no evident fault of Barthel's, the center of her story is incomplete. But she has told the rest of it so well that in the end it really doesn't matter.