EVIL, a concept long reviled by psychologists, may have been rehabilitated. A study of serial killers and mass murderers suggests that some criminals are so inherently bad that there is no other word to describe their actions.

The term evil has been derided because it is regarded as unscientific and carries unhelpful religious connotations. Psychologists argue the most awful crimes can usually be explained by mental illness.

However, this orthodoxy is now being questioned by Michael Stone, a professor of psychiatry at Columbia University in New York.

He looked at 500 British and American serial killers including Ian Brady, Myra Hindley and Fred West, to work out their motives. He found that while some were the victims of mental illness, others were perfectly sane — and had decided that they would enjoy killing.

Such behaviour, Stone says, defies any psychiatric explanation. Many killers are diagnosed as psychopaths but most psychopaths never commit violent crimes. This suggests that something extra is at work.

“Such people make a rational choice to commit terrible crimes over and over again. They are evil and we should be able to say that formally,” he said.

Stone and his team devised a 22-level hierarchy of evil derived from interviews, biographies and case notes of 500 violent criminals. They found many were suffering from illnesses such as schizophrenia. Others’ behaviour could be partially explained by abuse or events in their early lives which had left mental damage. Such people attained relatively low placings in Stone’s hierarchy, despite committing terrible acts.

Others, however, had no history of illness or other events to explain their actions and, said Stone, had made a rational choice to enact their fantasies for pleasure. Such people were placed at much higher levels in the hierarchy, with level 22 representing the ultimate in evil.

Stone includes West and Brady — but not Hindley — in this level, alongside some of America’s most notorious serial killers. They include Ted Bundy, convicted of two murders and suspected of many more in the 1970s, John Wayne Gacy, who strangled more than 30 boys, and Jeffrey Dahmer, a cannibal serial killer.

Stone accepts that the word evil has to be used carefully but says that for some there is no better description. “I am talking about the kind of people who torture their victims first before killing them and who may have a number of victims,” he said.

“In England people like Fred West and Ian Brady are clear examples but Myra Hindley might not be because she was to some extent led by Brady.”

The “mad or bad” debate is not a new one. Up until the last century people with mental illness were often considered to be possessed by the devil.

Sean Spence, a reader in psychiatry at Sheffield University, will be co-presenting a lecture on antisocial behaviour at the Royal Institution in London on Thursday. “The word evil has an outdated metaphysical ring to it. It would be no help to label someone as evil as it risks reinforcing their own fantasies and making them feel powerful and grandiose,” he said.

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