A judicial inquiry has found that the Garda Ombudsman was "mistaken" when it began a criminal investigation into the actions of gardaí following the death of a woman last year in a traffic accident in Co Donegal.

The Minister for Justice set up the inquiry after one of the gardaí under investigation, Sergeant Michael Galvin, was found dead in a garda station a week after he was questioned by GSOC investigators.

He appears to have taken his own life.

He and the other gardaí were cleared of all wrongdoing but had not been informed by GSOC.

Mr Justice Frank Clarke, a Supreme Court judge, also concluded that it was wrong that the gardaí had not been informed they were the subject of a criminal investigation but said GSOC's officers acted in good faith.

The judge described Sgt Galvin’s death as a tragedy.

He was one of three gardaí being investigated by GSOC after 33-year-old Sheena Stewart died in a traffic accident in Donegal on 1 January last year.

The father of three was interviewed by GSOC investigators who decided the next day he had no case to answer.

He was not aware that he had been cleared by GSOC of any wrongdoing.

The judicial inquiry established by the Minister for Justice found that GSOC was "mistaken" to begin a criminal investigation into the actions of the gardaí.

It said GSOC commenced a criminal investigation within 30 minutes of being informed of the case and the inquiry was "not satisfied" it had "available sufficient information" to make that decision.

It concluded that "it must have been the case" that at the relevant time "the circumstances then known did not appear to constitute a criminal offence".

It also concluded that "it was wrong" that the gardaí had not been informed of "the existence of a criminal investigation" and that "they were the subject of a criminal investigation".

In a statement released this evening, GSOC said: "The judge found that the decision to designate the fatality as a matter for criminal investigation was made too quickly after receiving the referral.

"However the inquiry found that the decision 'was taken bona fide and, in the light of the lack of clarity which is to be found in the legislation itself, the Inquiry has come to the view that it must conclude that the decisions respectively to recommend and designate the investigation as a criminal investigation, while mistaken, would not justify any action being taken against individuals concerned'.

"The report also clarified that 'while it views the decision to instigate a criminal investigation at the time when that decision was taken as having been mistaken, this should not be taken to mean that the inquiry feels that no criminal investigation at all could properly have been instigated'," added the statement.

However, the report further criticised An Garda Síochána's "internal communication" for the fact that the three gardaí did not know that statements they made to a garda inspector were for GSOC's investigation.

He also described as "highly unfortunate" the fact that an email intended to lead to the formal communication of criminal proceedings to the three gardaí "was inadvertently deleted" in Letterkenny Garda Station.

This he said led to the "extraordinary situation" that Sgt Galvin and one of his colleagues did not know they were under criminal investigation until they were told to present themselves for questioning and that another garda did not know until after he had been cleared.

Mr Justice Clarke partially blamed the lack of clarity in the legislation for some of the issues that have arisen and has recommended the law allowing GSOC to designate an investigation as a criminal investigation be reviewed as it is unclear.

The inquiry also recommended that GSOC reconsider how it conducts investigations, particularly as regards informing gardaí about the progress of criminal inquiries and that more detailed information be made available to gardaí.

It further recommended that GSOC consider the appropriateness of its policy of always sending a file to the DPP in cases involving a death as this might not always be necessary or justified.