Duffy went on trial in February 1988 and was convicted of two murders and four rapes, although he was acquitted of raping and killing Anne Locke. He was given a minimum tariff of 30 years by the judge, later extended to a whole life tariff by the Home Secretary. This however was to be rescinded by a European Court of Human Rights ruling, that later removed the right of politicians to reset sentence tariffs.
Duffy kept silent about having an accomplice until he decided he wanted to clear his conscience while undertaking a counselling session. He chose not to reveal any more information about his partner-in-crime until nearly 15 years later, in 1997, when he implicated Mulcahy. The police had suspected Mulcahy for years but had no evidence on which to convict him until Duffy’s confession.
Duffy also admitted his involvement in the attack on Anne Locke, although he could not be re-tried under the double jeopardy rule.
However, Mulcahy, a married father of four, had been tracked for several months by police prior to his arrest. DNA-tests, which were not yet in use during the original investigation, finally proved his involvement conclusively.