The officer, who was found not guilty by a jury last year, has initiated a legal action against the force in the High Court.
It is understood the officer, who is in his late 50s, is alleging An Garda Síochána failed to disclose key information about the investigation to the defence.
Sources familiar with the case say it “has the potential to cost the force a significant sum”.
The officer was suspended after he was charged with historical sex abuse, which he always denied, and was reinstated following his acquittal last year.
The jury at the Dublin Circuit Criminal Court trial heard the allegation first came to light after the complainant saw the garda appear on RTÉ’s
Crimecall programme as part of his work. He recognised the garda as the son of a woman who had minded him for a few years when he was a child.
The complainant, then aged 46, went to gardaí and alleged this man had sexually assaulted him on three occasions when he was around six or seven years old.
The garda, who cannot be named for legal reasons, pleaded not guilty to three counts of indecently assaulting the boy at a Dublin address and in a green area between April 1979 and May 1982. He was aged between 14 and 17 at the time.
The jury of nine men and three women returned not guilty verdicts on all three counts following a two-week trial.
The prosecution’s case was that the accused indecently assaulted the boy in the accused’s bedroom on two occasions by touching his penis.
It alleged that on a third occasion the accused called to the boy’s house on his bike, went for a cycle with the boy, and bought him a bar of chocolate before indecently assaulting him in a bush in a green area.
During the trial the accused man repeatedly denied he had ever sexually abused the complainant or that he ever called to the boy’s house.
“That never happened,” he told the jury. “I never touched that child.”
The defence submitted there were “frailties, inconsistencies, and contradictions” in the case, including the layout and appearance of the bedroom the complainant was allegedly abused in, which they submitted resembled the boy’s own childhood bedroom.
The defence also pointed to a number of childminders who looked after the boy shortly after the accused man’s mother, including one childminder who was let go because she was letting “undesirable” people into the boy’s house.
The trial heard the complainant “blocked out” the memories of the alleged abuse until 1994, when he said he encountered the accused man while he was out with friends one night in the city centre. He recognised the garda, who moved the man and his friends on, and then remembered the alleged abuse, the court heard.
Years later, the complainant was watching
Crimecall when the accused man appeared.