Enniskillen Crown Court heard that if Vincent McCaffrey had not come forward and admitted indecently assaulting the girl "there would be no case whatsoever" against him.
McCaffrey, from Carrowshee Park, Lisnaskea, was given a Combination Order of 12 months in prison followed by 12 months on probation. He has already spend three months in custody, the equivalent of a six-month sentence, and was told he has another six months to serve.
He pleaded guilty to indecently assaulting the girl on a date unknown between January 1, 1998, and December 31, 2001, when she was aged 11 or 12.
Prosecuting counsel, Mr. Robin Steer, told the court that McCaffrey had been at a drinking party in the girl's aunt's house in Enniskillen. He went into the girl's bedroom to give her a cigarette. He touched her over her clothes before penetrating her with a finger. She told him to stop.
Years later McCaffrey confessed to the crime and the police traced the victim but she said she did not want to make a complaint against him.
Defence barrister, Mr. Eoghan Devlin, said McCaffrey had expressly instructed him to apologise to the girl and her family and make it clear that nothing that was said in mitigation should take away from his genuine regret.
He referred to the "very unusual circumstances of this case coming to light" and said McCaffrey had taken the "very difficult step" of going into a police station and confessing to the crime.
"There would be no case whatsoever without this man's admission," he submitted.
Mr. Devlin said it appeared that as a young man McCaffrey became dependent on alcohol and drugs. He was involved in offending of a fairly serious nature and his life "snowballed out of control".
He told the court: "There is a short period of offending after this incident but it does seem to me this was a watershed moment in this man's life."
He said McCaffrey came from a fairly isolated background and remained isolated.
"These offences carry a stigma, which he is all too well aware of," said the barrister.
"He regrets his actions, apologises for them and accepts he has to be punished," Mr. Devlin added.
Judge Geoffrey Miller told McCaffrey this was a serious sexual assault committed when McCaffrey was under the influence of drink and drugs.
"You told police you were aware of what you were doing when you were doing it," he added.
He said that on the other hand he could think of very few instances during his 30 years as a barrister and judge where someone "can palpably be shown to demonstrate true remorse in the way you have".
He referred to the "very troubled and tragic background" that led McCaffrey into a downward spiral. Between 1975 and 2003 he was breaking the law on a regular basis, with convictions for offences of violence, robbery, public disorder and predominantly burglary. As a result he had served lengthy periods in prison.
The judge said McCaffrey had been struck by what he had done to the girl and apart from robbing a relative in 2003 had not been brought before any court, and that was set against a background of him having a lengthy criminal record. He had realised by virtue of what he had done that he had to address issues in his live, drink and drugs. He received support from the Salvation Army and lived in one its homes for four years. It was during that time he took the decision to go to the police and tell them "what you had done on that night to that child".
He said it was clear that when the girl, who is now a mature woman, was contacted she acknowledged what McCaffrey had done "but had made a life for herself and wanted to put what happened that night behind her".
Imposing a combination order for two years, the judge also disqualified McCaffrey from working for children for five years and ordered him to remain on the Sex Offenders' Register for 10 years.