In September 1994, I went with Ian Jack, the then editor of the Independent on Sunday, to present awkward questions to a senior officer at New Scotland Yard. A few days earlier, Mr Justice Ognall had accused his force of seeking to incriminate a suspect with "deceptive conduct of the grossest kind". Its attempt to convict Colin Stagg of the murder of Rachel Nickell was "misconceived", "wholly reprehensible" and "redolent with danger".
"You blundered," we said.
"No. Absolutely not."
The authoritative expression on his face has stayed with me ever since. He was convinced that Stagg was guilty and we had to pinch ourselves to stop him convincing us as well. He showed no hint of doubt, no sign of suppressed panic or remorse.
On the contrary, he looked down on his critics from a position of knowing superiority. "Exactly who is the fool here?" he seemed to ask. Not the police, led by Detective Inspector Keith Pedder and supervised by Assistant Commissioner Ian Johnston, who told a pretty constable to turn herself into "Lizzie James", a sadistic temptress who might seduce admissions from the lonely Stagg.
Not Dame Barbara Mills, then Director of Public Prosecutions, who thought the covertly collected evidence was worth presenting to a court, even though when "Lizzie" said she enjoyed hurting people, all Stagg could say was: "Please explain, as I live a quiet life. If I have disappointed you, please don't dump me. Nothing like this has happened to me before."
To our senior officer, his colleagues and all the tame hacks who went along with them, the real fool was the judge who let off a guilty man on a technicality.
When the police go for the innocent, the guilty go free. We now know that while detectives encouraged the tabloid press to spend years pillorying Stagg, and tabloid television demanded he sit lie detector tests, the real killer grew ever more dangerous. Robert Napper murdered Rachel Nickell in front of her son in July 1992. In November 1993, he broke into the flat of Samantha Bissett and stabbed her to death, then sexually assaulted and murdered her four-year-old daughter Jazmine. How many women he attacked before the courts finally jailed him in the autumn of 1995 is an open question. Chastened officers believe he may be responsible for assaults on about 80 victims, including rapes, and possibly other murders.
Dozens of women may have paid a price - in some cases the highest price - for the smug look on my senior officer's face and the cocksure accusations of his followers in the media.
Paul Britton, a forensic psychologist practising the fashionable discipline of offender profiling, gave them their self-confidence, although even now commentators do not understand the full brazenness of his behaviour.
Operating on his instructions, "Lizzie" told Stagg to say anything because "my fantasies hold no bounds and my imagination runs riot. If only you had done the Wimbledon Common murder, if only you had killed her, it would be all right".
To which Stagg, replied: "I'm terribly sorry, but I haven't."
Detectives discounted his denial, which was convincing when you consider he had an incentive to say anything that might please his strange girlfriend. The point of the undercover exercise was not to extract a confession from Stagg, as no judge would have allowed a jury to hear evidence from a honey trap. Britton's pseudo-science aimed at securing more than a mere admission. He believed that his academic insights had given him the psychological profile of the killer.
Detectives set "Lizzie James" on Stagg to see if he matched Britton's description of a murderer, who was excited by his victim's fear and had a "deviant interest in buggery". When Britton ruled that the local loner did, the police believed him. Police say that Britton also told them that the murders of Rachel Nickell and Samantha and Jazmine Bissett were not the work of the same man, although Britton disputes this.
The specifics of Britton's folly are gruesome enough. As professor David Canter of Liverpool University said at the time, he barely mentioned the most striking and revolting aspect of the case: that the killer murdered Rachel Nickell in front of her child. As William Clegg, Stagg's QC, added at the trial, the transcripts of the conversations between his client and "Lizzie James" showed only that Stagg was a friendless man going along with a domineering but beautiful woman.
But dwelling in the detail misses the wider point. Just as dissenting economists are asking by what right their conventional colleagues demand to be taken seriously when no more than a handful warned of a coming banking crisis, so Parliament and the public should be wondering by what right psychologists demand a hearing.
It is not a reputable profession. The British Psychological Society dismissed all charges of misconduct against Britton in 2002, and no-one else has held him to account for what he did to Stagg and, indeed, to "Lizzie James", who went on to suffer a nervous breakdown.
If psychology is a reliable science - and frankly I doubt its credentials - it is a science "redolent with danger", to use Ognall's words. Britton would never have impressed detectives if he had said that Stagg was a bit of a weirdo. When he dressed up that same thought in psychological language and talked of "deviant interests" and "sexual dysfunctions", he sounded fatally convincing.
A cold-case review team caught Napper because it found a DNA sample, which the assiduous technicians at LGC Forensics proved beyond reasonable doubt came from Rachel Nickell's killer. Their evidence was the anthithesis of the psychologist's speculative theories: hard, testable and incontrovertible.
Genetic fingerprinting catches the guilty and frees the innocent. Psychological profiling traps the innocent and sends the guilty out to kill again. The Home Office might offer a small redress to the raped and murdered women if it resolved in future to tell the police to stick to what works.