The Metropolitan Police in west London initiated an urgent investigation, named "Operation Hart", to apprehend the perpetrators.
[3] On the evening of 29 December 1985, Alison Day, aged 19, was on her way to meet her boyfriend at his place of employment at a desolate trading estate close to Hackney Wick station.
Duffy and Mulcahy had been driving around several railway stations and ended up at Hackney Wick where they saw Day exit the train.
Day fell from the bridge into the canal, but was able to swim to the bank where Duffy and Mulcahy pulled her from the water and then to a wasteland where she was strangled to death with her blouse.
He then drew a link with the murder of Tamboezer when he spotted that a belt and twig in a scene photo were the parts of a tourniquet ligature.
A month later on 18 May 1986, Anne Lock, a 29-year-old secretary at London Weekend Television was abducted and murdered after she got off a train at Brookmans Park railway station, Hertfordshire.
It was the first such investigation to utilize basic computers and an early version of HOLMES (Home Office Large Major Enquiry System).
Duffy, a martial arts exponent and former railway carpenter, was identified by Detective Superintendent John Hurst as a suspect.
His experience with traditional bow saws linked him to the unusual method of strangulation using a self-fashioned tourniquet, and his knowledge of the South Eastern railway system was part of his former job.
[6] To help their inquiries, the police brought in a psychologist from the University of Surrey, David Canter, who was working in the field of geographical psychology at the time.
There had been no previous use in Britain of "psychological offender profiling" as it was known, but something fresh was required as two women and a child had been murdered and numerous others raped, with little progress being made.
[10] Following the trial, much was made of the psychological profile constructed by Canter, as Duffy fitted 13 of the 17 observations he had predicted regarding the attacker's lifestyle and habits.
Bolland told her that real progress could be made if Duffy received counselling; this was arranged, and in June 1998 he agreed to start making full, proper, detailed admissions to the police.
[3] Following Duffy's claims, Mulcahy—a married father of five—was tracked for several months by police, then arrested in February 1999; DNA tests (which were not yet available during the original investigation) conclusively proved his involvement, supported by evidence from a search of his home.
A complaint to the solicitors, who had written to prisoners who were not their clients, led to claims that the letters were an error made by a clerical worker.
Mulcahy, described as "smug and arrogant" in the witness box, denied all allegations and said that Duffy was lying, that the DNA had been planted by the police, and a fingerprint on the tape used during a rape was not his.
[13] After Mulcahy was found guilty, police re-opened investigations into hundreds of unsolved rapes and murders across the country, suspecting that the two men may have committed more offences than those Duffy confessed to.
[12] Detective Superintendent Andy Murphy said that he suspected Mulcahy had committed other acts of violence against women both on his own and with Duffy, and encouraged any surviving victims to come forward.
While not in the public media, Bolland, who had been involved in the case from beginning to end, starting at a junior rank, and played a significant part, wrote a detailed article of his experience in the journal Medicine, Science and the Law in 2002.
The Railway Killers, a documentary about the case with the dramatisation of the murders and interviews with key figures, was broadcast on Channel 5 in three parts, starting on 16 August 2021.