A spokesman for the University of California at Los Angeles, where West was in charge of the Neuropsychiatric Institute for 20 years before his retirement in 1989, said he died on Saturday of cancer at his home in Los Angeles.

West frequently worked as a court-appointed psychiatrist. After examining Ruby, the killer of President John F. Kennedy's assassin, Lee Harvey Oswald, West concluded Ruby was suffering from ``major mental illness precipitated by the stress of (his) trial.''

The psychiatrist was also one of four experts who examined newspaper heiress Patty Hearst, who was kidnapped by the so-called Symbionese Liberation Army and who later joined its ranks as a bank robber.

The panel found her sane and fit to stand trial, but West wrote that she was ``psychologically damaged as a result of torture by the SLA.''

The experts also urged that Hearst receive treatment for her mental illness before her 1976 trial, but the court ignored the recommendation. ``The government finished the destruction of her life started by an anti-government group,'' West said after Hearst was convicted. Her prison sentence was commuted by President Jimmy Carter in 1979.

A civil rights activist, West was the first white psychiatrist to go to South Africa to testify on behalf of black prisoners during the apartheid era.

During the Korean War he studied brainwashing and torture. He said at the time that American prisoners of war had falsely confessed to engaging in germ warfare because their captors had instilled a sense of guilt in them through solitary confinement, prolonged sleeplessness and physical abuse, which he called the classic tools of brainwashing.

In an interview with the Los Angeles Times, West said the behaviour of cult members and kidnapping victims was driven by the ``three 'Ds' - debility, dread and dependence.''

"A prisoner is debilitated by inactivity, by sleep loss, or worse, by physical harm. He is filled with dread by constant threats of pain or death or harm to his family. He is rendered completely dependent upon his captors for information, food, shelter, life,'' West said.

West, who was born the son of poor Russian Jewish immigrants in Madison, Wisconsin, is survived by his wife Kathryn, son John and daughters Anne and Mary.