Andrew Hannam, who was tracked down in the UK earlier this year following a cold case review by the States police, subjected the woman to three assaults during the attack on 25 February 1995.
Appearing in the Royal Court via video-link from a secure hospital in the UK, the 44-year-old on Tuesday pleaded guilty to attempted rape and two counts of indecent assault.
The defendant, who spoke only to confirm he could hear the court, will remain in the hospital until he is sentenced by the Superior Number, which convenes only for the most serious offences, on 21 January.
Hannam was arrested in England in October, following a cold case investigation codenamed Operation Cortico, and was brought back to the Island to be charged.
Deputy Bailiff Tim Le Cocq warned the defendant that the nature of his offences meant that he faced a custodial sentence.
He also ordered the preparation of a psychological report.
Jurats Paul Nicolle and Sally Sparrow were also sitting on the case.
In April, Joao Pedro Pacheco Santos (46) was jailed for seven years for a violent and prolonged sex attack against a 21-year-old victim in 1998 which was one of several cold case investigations carried out by the States police.
Detective Superintendent Stewart Gull, who played an integral role in the case, said offenders should be ‘fearful’ because advancements in DNA technology and forensic techniques meant officers had the powers to trace more undetected criminals.
‘Offenders should be worried, they should be fearful,’ he said.
‘It does not matter how long it takes, but early one morning they might just get a rude awakening with police officers at the door.’
