The pioneer of criminal profiling in Britain has switched sides to say that a man he helped to jail for life for murdering his wife is innocent.

Eddie Gilfoyle was prosecuted after David Canter, a psychology professor, told police that his hanged wife’s suicide note betrayed signs of having been faked. But research prompted by the case into the difference between genuine and false suicide notes has persuaded Professor Canter that Paula Gilfoyle, 32, was, indeed, the sole author of her final words.

Now campaigners for the jailed husband are hoping to use Professor Canter’s analysis of the suicide note as part of a fresh appeal.

On a June evening in 1992, Paula Gilfoyle’s body was found hanged in the garage of the home in Upton, Wirral, Merseyside, that she shared with her husband.

Mrs Gilfoyle, who worked in a local factory, was eight months pregnant and presented a cheery front to the world. But the long suicide note that she left spoke of a feeling of failure and unhappiness, and hinted at strains in her marriage. She told her husband not to blame himself, and even suggested that the baby was not his. There is an overwhelming feeling of guilt and self-blame in the note.

Friends and relatives refused to believe that she could have killed herself. They insisted that she had no cares and was looking forward to the birth of her first baby. Suspicion soon turned on her husband. Some work-mates told police that she had said that her husband, a hospital porter, had persuaded her to write a bogus suicide note as part of a course that he was taking on suicide. No such course existed.

However, Professor Canter points out, in a 10,000-word report on the case, that for the bogus suicide plot to have worked Gilfoyle would have had to persuade his wife to climb a ladder in the garage and allow a noose to be placed around her neck. There were no signs of force on her body.

Gilfoyle has always protested his innocence of what was portrayed as a calculated, evil plot to make his pregnant wife’s killing look like suicide.

When Merseyside police began to investigate Mrs Gilfoyle’s death, they consulted Professor Canter, who had been the first psychological profiler to be used by British police and who shared their doubts about the note.

His evidence formed part of the prosecution case, though it was never heard by the jury. He nonetheless believes that it helped to reinforce prosecutors’ determination to press ahead against Gilfoyle, who was convicted unanimously of murder in July 1993.

Professor Canter used a technique of linguistic analysis to try to establish whether Mrs Gilfoyle had composed her note. Police suspected that her husband had dictated it to her. But studies since, including one supervised by Professor Canter, have shown that errors can be produced by using simple word counts as the main basis for deciding authorship.

By chance, a couple of years after the conviction, Professor Canter moved to Merseyside, taking a post at the University of Liverpool. There, he came into contact with Gilfoyle’s relatives and eventually met the prisoner himself. “He wasn’t that creative an individual,” Professor Canter said. The academic then began looking closer into the science of suicide notes.

The most pertinent study was conducted 50 years ago by the founders of the Los Angeles Suicide Prevention Centre, Edwin Schneidman and Norman Farberow. The two psychologists, pioneers in suicide prevention, compared genuine suicide notes with artificial ones written by people who had never been suicidal.

Their purpose was to look for ways to stop people taking their own lives. But Professor Canter made a study of those 1950s notes, along with other samples, to seek clues to how a genuine suicide note could be distinguished from an imagined one. It became clear that it is difficult to simulate the elements in a real suicide note. Professor Canter now uses Mrs Gilfoyle’s final handwritten lines, beginning “Dear Eddie” and ending “Goodnight and God bless, love Paula”, in his lectures.

“It is my opinion that the suicide note was written, unaided, by Paula Gilfoyle,” he said. “That this intention was genuine is difficult to determine, but the way in which the note appears to be the culmination of months of thinking of various possibilities for dealing with her situation, and indicates so directly that Paula could see no other way, is consistent with a very real determination to kill herself.”

Gilfoyle’s brother-in-law, Paul Caddick, a retired police sergeant who found Mrs Gilfoyle’s body and now runs the miscarriage of justice campaign, praised Professor Canter.

“He is a brave man,” Mr Caddick said. “We are very pleased he has come on to the defence side because he is a man of integrity. Obviously, for a long time, Eddie didn’t like him. When he came on to our side he said, ‘The bastard, he should’ve said the right thing in the first place’. But now he realises it was a dreadful mistake.”

Gilfoyle has already lost two appeals against conviction but his new legal team at Birnberg Peirce is preparing evidence to bring before the Criminal Cases Review Commission.

Merseyside Police said: “There was a lot of other evidence heard by the jury and he was convicted on that evidence.”

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