Mr Britton, head of Trent Forensic Psychology Service, worked with police on the undercover operation which provided the main plank of evidence against Colin Stagg, who was charged with murdering Ms Nickell on Wimbledon Common in July 1992 in front of her two-year-old son Alex .
Mr Stagg was acquitted at the Old Bailey last Wednesday when the case against him collapsed because the judge rejected evidence from the operation after hearing that an attractive undercover woman police officer tried to entice Mr Stagg to confess in a lengthy exchange of pornographic correspondence.
Mr Justice Ognall described the operation, co-ordinated by Mr Britton, as 'wholly reprehensible' and 'deceptive conduct of the grossest kind'.
Mr Britton, 48, who has been involved in up to 100 police investigations, responded for the first time yesterday in a statement: 'I am confident that I have acted entirely professionally throughout my involvement as an adviser to the Metropolitan Police in their investigations into the murder of Rachel Nickell.'
Had the case gone ahead it would have been the first time that a psychological profile had been used as evidence of identity. But Mr Justice Ognall described the use of such evidence as 'redolent with considerable danger'.
Some of Britain's leading criminal psychologists yesterday also strongly criticised Mr Britton's part in the investigation. Professor David Canter, one of the leading authorities on forensic psychological profiling, said: 'As a professional psychiatrist I think the judge's views were emphatically expressed and eminently sensible.'
Dr Barry Irving, head of psychology research at the Police Foundation in London, said the Nickell case was 'a disaster waiting to happen' since the Eighties. 'The clinical approach Britton was using can produce more brilliant results but also can be more disastrously wrong.'
Mike Berry, a leading forensic psychiatrist, said yesterday that in the Nickell case Mr Britton had moved on from offender profiling to case management: 'It is a different issue altogether. I'm not an advocate of entrapment because I don't think that's appropriate. But there was a possibility it could have been successful.'
Yesterday Ian Ryan, Mr Stagg's solicitor, criticised the police for failing to assess Colin Stagg's mental stability, and the impact of the undercover policewoman's letters.
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