A 37-year-old Dublin man has been acquitted of the sexual assault of a woman in a busy late night bar, by direction of the judge in his trial at Dublin Circuit Criminal Court.
The judge said gardaí should have questioned another man present on the night.
Donal Geoghegan, of Oakdale Park in Ballycullen, had pleaded not guilty to sexually assaulting the woman on 21 November 2015.
The woman had been collecting glasses at the end of the night when she felt someone's hand at the top of her thigh and described how it moved to her vagina.
Judge Cormac Quinn ordered the jury to acquit Mr Geoghegan because of the "infirmity" of the State's evidence.
The judge cited the report of the Morris Tribunal and he said garda investigations should be carried out in an open-minded and objective manner.
He said CCTV evidence showed another man, described as "Mr X", near the complainant at the time of the alleged offence and it was possible he had touched her.
The judge said this man had never been investigated by gardaí.
Judge Quinn said he was satisfied that the mere fact a complaint was not made against him was not sufficient reason for not investigating this other man.
He said if the case went to the jury to decide, he would be bound to tell them gardaí should have sought statements from witnesses.
The defence described "Mr X" as behaving in an extremely tactile way towards four or five women, one of whom he touched "in a covert manner".
The complainant in this case said she did not see who had touched her. Judge Quinn said she described turning around and seeing the defendant looking at her in a blank, indifferent way.
He said the woman told the jury she knew in her gut it was Mr Geoghegan who had assaulted her.
But the judge told them that was not evidence and could not be relied on.
He said the jurors could not convict Mr Geoghegan when the activities of Mr X had not been investigated.
He said in CCTV footage, Mr X could be seen placing his hands on two women's arms and hair, patting a third woman's head and putting his mouth towards a fourth woman's arm.
Senior Defence Counsel Michael O'Higgins had suggested during the trial that the garda investigation was "rank with incompetence", a suggestion denied by Sergeant Joanne McCormack under cross-examination.
Sgt McCormack told Judge Quinn gardaí did not try to identify any of the other people in the bar that night.
Mr O'Higgins told the court that Mr Geoghegan wanted to make an application for costs.
That issue will be heard on 11 January.