Mr Justice Ognall ruled that a seven-month undercover operation used to gather the profile was unfair, a breach of a defendant's right not to incriminate himself, and advised the police not to base future cases on profiling because it had not achieved general acceptance as a science.
A formal verdict of not guilty to the murder in July 1992 was returned by the judge on Colin Stagg, 31, after the prosecution said they had no case other than the psychological profile.
The judge unequivocally criticised the operation as 'misconceived'. He said: 'I am afraid this behaviour betrays not merely an excess of zeal, but a blatant attempt to incriminate a suspect by positive and deceptive conduct of the grossest kind. Any legitimate steps taken by the police and the prosecuting authorities to bring the perpetrators to justice are to be applauded, but the emphasis must be on the word legitimate. A careful appraisal of the material demonstrates a skilful and sustained enterprise to manipulate the accused, sometimes subtly, sometimes blatantly.'
He said that there had never been any chance that the exercise could have cleared the suspect. It had been designed solely to incriminate him.
Paul Britton, a forensic scientist, had deduced the likely characteristics of the killer from the scene, then compared them with fantasies an undercover police officer had extracted from Mr Stagg by posing as his girlfriend. Rachel Nickell, 23, had been stabbed 49 times in front of her two-year-old son.
Through letters, telephone calls and eventually meetings over seven months, the undercover officer encouraged the suspect to develop his fantasies to match the profile.
Scotland Yard last night defended the use of undercover operations, but declined to comment in detail on this case or on psychological profiling until senior officers had studied the judge's comments more carefully.
The Crown Prosecution Service, which had advised the police at every stage in the process, said it was satisfied the prosecution had been 'properly brought in accordance with the code for Crown prosecutions'.
Outside court, Mr Stagg, who spent more than a year in custody, said: 'I am innocent and I have always been innocent of this horrible crime. My life has been ruined by a mixture of half-baked psychological theories and some stories written to satisfy the strange sexual requests of an undercover police officer. The judge recognised there was never any evidence against me - no forensic evidence, no confession evidence, nothing at all. I now intend to take proceedings against the police and the psychologist, Paul Britton, for the anguish and distress I have suffered.'
As the judge concluded his remarks, the victim's mother, Monica Nickell, sat in the public gallery with tears streaming down her face. Afterwards, her husband, Andrew, defended the police operation: 'The police undertook this operation because they felt it was the only way to prove or disprove their suspicion that Colin Stagg was the murderer.
'There was no physical evidence, only strong circumstantial evidence. What were the police to do? Were they to let a man whom they suspected and believed was guilty of hideous murder to roam free? What choice did they have?'
World of fantasies, page 3
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