The vicious attacks started in the early eighties. Initially acting as serial rapists, John Duffy and David Mulcahy had brutally assaulted and raped dozens of young woman, before making their first fatal victim. Alison Day was followed by the pair of assailants in December 29, 1985, and eventually killed after being raped several times. Nonetheless, Duffy and Mulcahy began to act more sporadically, and this fact caused some difficulties to the police, that was having a hard time to connect all the crimes to a single suspect.
As the rape and murders had continued, though, the police set up several different investigative task forces, to align everything correctly into a diagram of cohesive patterns. When different cases were conclusively linked to a single perpetrator, they were classified together. Since John Duffy already had a criminal record, registered when he was accused of raping his own wife, he was enlisted as a main suspect, among thousands of others.
As the investigation advanced, it became increasingly clearer that John Duffy was, beyond any question, the real offender. When the police collected enough evidence to prove that he was, indeed, the offender beyond any reasonable doubt, he was imprisoned and sent to justice. Nonetheless, by virtue of several clues left at the crime scenes, as well the nature and the circumstances surrounding the rapes and the murders, it became clear that Duffy hadn’t committed all those crimes alone. Probably he had an accomplice, something the police investigators had already suspected. Despite his reluctance – Duffy and Mulcahy had some sort of a mutual agreement, like a “code of honor” that inherently left implicit the fact that if one of them was caught by the police, there would be a refusal to reveal who was the accomplice – Duffy eventually agreed to name his partner in crime, probably bittered by the fact that, while he was in prison, his former murderous associate was free to live his life exactly as he wanted. Nonetheless, it took a long time, before Duffy decided to reveal to the police who his accomplice really was. Imprisoned in 1986, it would take more than a decade for Duffy to speak to the officers that his partner in crime was his childhood school friend, David Mulcahy, who was finally arrested in 1997. After a lot of evidence was gathered, the case was closed, as it was finally proved that John Duffy and David Mulcahy were the Railway Killers. To this day, David Mulcahy still affirms he is innocent, and runs a website that contests the investigations.