John Duffy and David Mulcahy

John Francis Duffy (born 1958) and David Mulcahy (born 1959) are two British serial rapists and serial killers who together attacked numerous women and children at railway stations in southern England during the 1980s.

Their crimes are often referred to as "the railway murders", and they are often referred to as the "railway rapists" or the "railway killers"; Duffy, once identified, was referred to in the press as the "railway murderer" or "laser eyes".

Mulcahy was a lifelong friend from whom Duffy had been inseparable since their days together at Haverstock School in North London.

Whilst in school they were once excluded after being found laughing and covered in blood, after bludgeoning a hedgehog.

In 1982, a woman was raped by two men near Hampstead Heath railway station.

Eighteen more women were attacked over the next year, mostly late at night in dark, quiet places often near railway stations in and around North London, especially Hampstead, Barnes and other places.

Further attacks occurred during 1984, and then three women were raped on the same night in 1985, in Hendon.

The Metropolitan Police in West London initiated an urgent investigation, named "Operation Hart", to apprehend the perpetrators.

The women described their attackers as a short ginger-haired man and a larger man.

DNA technology was not then available, but some suspects could be eliminated by blood grouping: one attacker, believed to be the ginger-haired man, was an "'A' secretor with a certain PGM factor of his blood".

Unlike DNA, many people share the same blood grouping, so this evidence could eliminate suspects but not identify the offenders.

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.

After she stopped at a telephone box, it is believed she took a wrong turn heading down to the canal and into the path of Duffy and Mulcahy.

Duffy then threatened her with a knife and both men sexually assaulted her.

The two men then forced her to walk across live railway lines to the parapet of a bridge.

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.

Her body was sunk into the River Lea using discarded cobbles (granite setts) placed into her coat pockets.

The Metropolitan Police in east London set up a further separate investigation, Operation Lea.

Police further stepped up their search for the attacker who had been nicknamed by the press the "Railway Rapist".

The murder of Day changed this name to the "Railway Killer", a tag reinforced by the rape and murder of 15-year-old Dutch schoolgirl Maartje Tamboezer in West Horsley in Surrey on the afternoon of 17 April 1986 after knocking her from her bicycle with a wire that had been tied between two trees.

As well as suffering rape and strangulation, Tamboezer had been repeatedly struck in the head with a rock and her body was set on fire.

Surrey Police set up Operation Bluebell.

Meanwhile, the Day murder inquiry was taken over by Detective Superintendent Charles Farquhar (a highly experienced east London murder investigator) and he linked that murder with the previous railway rapes.

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.

This heralded the first multi-police force murder inquiry (Operation Trinity) since the badly executed Yorkshire Ripper inquiry.

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.

He was known to police as he had been charged with the rape of his estranged wife.

He is known to have believed that rape was a "natural male instinct".

A rare type of string called 'somyarn' was found in his parents' house.

This linked him to the second murder victim.

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.

David Mulcahy was also questioned, owing to his close friendship with Duffy, but victims were still traumatized and unable to pick him out of an identity parade (at that time, identity parades required the victim to physically touch the offender and get close to him).

Mulcahy was released for lack of evidence.

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.

Canter examined the details of each crime and built up a profile of the attacker's personality, habits and traits.

While this continued, another attack took place, when a 14-year-old girl was raped in a park.