A life of crime: Professor David Wilson - trying to understand why serial killers kill

The Professor of Criminology at Birmingham City University is one of the country's foremost experts on serial killers. Having assisted the police with offender profiling in cases such as the Ipswich prostitute murders, he is the author of books such as A History of British Serial Killing, and co-author of Hunting Evil: Inside the Ipswich Serial Murders.

But there's one letter that Prof Wilson doesn't have. Peter Tobin, jailed in 2007 for the murder of Angelika Kluk, and since convicted of the murders of missing teenagers Vicky Hamilton and Dinah McNichol, has not responded to his approaches. Tobin has declined to comment on Prof Wilson's latest research which claims that he is also Glasgow's most notorious serial killer, Bible John.

Prof Wilson, who grew up in Carluke, near Glasgow, outlines his argument in his new book, The Lost British Serial Killer, written with Sky TV journalist Paul Harrison, in which he reexamines the facts of the original investigations, interviews people connected with the case and applies modern profiling techniques.

The man who has gone down in history as "Bible John" killed three women – Patricia Docker, 25, Helen Puttock, 29 and Jemima McDonald, 32 – whom he met at the Barrowland Ballroom in 1968 and 1969, assaulting them and strangling them with their own tights. Despite one of the biggest manhunts in Scottish police history, the crimes remained unsolved for 40 years.

Prof Wilson, 52, says it gave him satisfaction to work on Glasgow's most famous unsolved mystery. "Bible John was definitely a presence in my childhood, parents, aunts, uncles, grandparents, neighbours, would talk about him," Wilson says. "He was a bogeyman figure. At first I was interested in Peter Tobin because he had commited murder at 60, and murder is usually a young man's business. I wanted to see when that offending began. Then it seemed that his personal story crossed over into the story of an iconic set of murders in Scotland when I was growing up."

It was sitting in Chelmsford Crown Court, listening to Tobin being tried for the murder of Dinah McNichol, who disappeared while hitchhiking home from a music festival in Hampshire in 1991, that Prof Wilson had "a Eureka moment". "I was listening to a witness giving evidence about sharing a car journey with his girlfriend Dinah McNichol and Peter Tobin, and I realised that the pattern of conversation was similar to the pattern of conversation in terms of the taxi journey across Glasgow given by the sister of Helen Puttock in the Bible John investigation. At that moment, I really did think: 'My gosh, this guy is Bible John'."

Tobin was already a convicted serial killer and sex offender (he had completed a sentence for an attack on two young girls). The bodies of teenager Vicky Hamilton, who disappeared near her home in Bathgate in 1991, and Dinah McNichol had been found buried in the garden of a house in Margate where he once lived. Everything Prof Wilson knew about serial killers told him there would be more victims. The only question was: how long ago?

The key witness in the Bible John investigation was Jeannie Williams, Helen's Puttock's sister, who shared a taxi with Helen and the man calling himself "John" from Barrowlands back to Scotstoun in 1969. It is from her description that the image of Bible John – tall, dark, religious, superior – has come down to us. And it was she who worked with Lennox Paterson, deputy director of Glasgow School of Art, to create the artist's impression which became the mysterious man's enduring image.

But there were problems with Prof Wilson's theory. "Jeannie Williams described Bible John at over 6ft, while Tobin is around 5'8 or 5'9. Also, there was a DNA sample (of semen from Helen Puttock's tights] so I always thought this would rule a suspect in or out very quickly. By interviewing detectives who worked on the Bible John case I was able to find out that the DNA sample was not appropriately stored and is therefore worthless.

"They also told me that Jeannie Williams' first words to them were that she had been completely drunk when she shared the taxi. Bible John grew in size and stature and appearance every time she described him, he became almost Hollywood. So I began to think, hang on a minute, this does make some sense of the dissonant parts of the evidence that has come down to us.

"What struck me acutely was that nobody really concentrated on the first murder, because there was this compelling witness in the third case. Yet as a criminologist who has worked with and studied serial killers, I know how important the first murder is, so I wanted to return to the murder of Pat Docker and see what that could tell us."

He and Harrison traced Tobin's first wife Margaret Mackintosh, with whom he was living in Glasgow in the late 1960s. She told them about the abuse and sexual sadism she suffered at his hands. She was also able to tell them about his travels. At a time when few people made long journeys, Tobin moved regularly between Scotland and the South of England, a crucial factor in allowing him to remain beyond the reaches of the police.

"And there were details which were so clear. Jeannie Williams said that Bible John gave a surname, but she wasn't quite sure what it was, she thought it was something like Templeton or Sempleson, and we subsequently learned that one of the pseudonyms used by Peter Tobin was John Semple. If that was in a TV script, people would say it's too far-fetched."

Despite assembling a battery of evidence he says it is unlikely police will reopen the cases and bring Tobin to trial for the murders. "I suppose the long and short of it is, is it in the public interest? He is never going to be released from jail, he's going to die in prison, so there's no further punishment that one could give to them."

But Prof Wilson does contend that no serial killer could remain undetected for so long today due to advances in forensic science and the co-operation between different police forces. If Peter Tobin is Bible John, he has been slaying for longer than any other serial killer in British history, but he is the last of his kind.

Prof Wilson, offering me tea in his office overlooking the university campus, is a genial man to work in such a grisly area of expertise. A graduate of Glasgow and Cambridge, he began his career in the prison service, becoming the youngest prison governor in the country when he was 29. Having designed and run the two units for the 12 most dangerous prisoners in the country, he came into contact with most of the serial killers in British jails.

And they don't live up to the Hannibal Lecter stereotype, he says, with a wry smile. "People think that the serial killers are all going to be interested in Florentine architecture, fine foods and wines and are going to discuss with me the latest article in the British Journal of Forensic Psychology. Either that or that they're going to be very scary people who will do me damage.

"I've never been scared physically of any of the serial killers that I've met or worked with. The emotion I feel most readily is depression. What one encounters is either their failure to acknowledge that they have done harm to others, or their enjoyment of the fact that they have done harm to others. And both of those things are ultimately incredibly depressing."

Neither do they provide a convenient answer to the question which fascinates the readers of many best-selling true crime books: why do serial killers kill? "If they do speak about their motivation it is usually either so specific to them or so generic and banal that it could be applied to each and every one of us. I always say, don't try to understand the phenomenon of serial killing from the perspective of the motivation of the serial killer, try and understand the phenomenon from who it is the serial killer is able to kill.

"Overwhelmingly, they only kill from within five groups of people: the elderly, prostitutes, gay men, children and the group I call 'runaways and throwaways', kids leaving home. I always say to my students, look at access and opportunity first and worry about motivation last of all."

Certainly, this bears out in the history of British serial killing, from Jack the Ripper to the Moors murderers, Denis Nilsen to Ipswich murderer Steve Wright. Harold Shipman, the Manchester GP, known in the tabloids as "Dr Death", killed more than 200 elderly people by administering lethal doses of drugs while visiting them in their homes.

Bible John's victims were vulnerable because they were contravening the social mores of the day – young married women going out alone to the Barrowlands Over-25s night. This inhibited witnesses from coming forward, and in case of Pat Docker, sent the police on a false trail: she had lied to her family, saying she was going to another, more upmarket, dance hall.

"We, the public, create the conditions in which serial killers operate," says Wilson. "Our moralising about women who sell sexual services creates the circumstances which can be exploited by people who want to do those women harm. Our homophobia creates the circumstances in which gay men are the regular targets of serial killers. Our public policy which renders the elderly voiceless and isolated creates the circumstances that people like Shipman can exploit.

"What I try and do within the true crime genre is to say, OK, people are fascinated by offender profiling and serial killers. Let's harness that fascination to good public policy outcomes."

• The Lost British Serial Killer: Closing the case on Peter Tobin and Bible John, by David Wilson and Paul Harrison, is published by Sphere, priced 6.99. David Wilson will be at Waterstones, Sauchiehall Street, Glasgow, on Tuesday 6 July at 6:30pm, for information call 0141-332 9105