Who recalls that she was in Letterkenny garda station on the night of 4 December 1999 when a number of suspects in the "murder" of Richie Barron were being interviewed? Who remembers what she subsequently said in a statement about the activities of her colleagues on that occasion? And who remembers how she was treated by garda authorities in the wake of that statement?

Her story is a compelling one and, in the wake of last week's acquittal of suspended detective sergeant John White on charges of planting a gun, is worth retelling because of what it suggests about how garda authorities deal with whistle-blowers from within their ranks, officers who for whatever reason decide to point the finger at colleagues and say: "I saw you do wrong".

In Letterkenny station that night with Fowley and other gardai were Frank McBrearty junior and Mark McConnell, who had been identified as suspects by local officers. They were, of course, entirely innocent.

According to a statement made by Fowley and subsequently read into the record of the Dail by the former Fine Gael TD Jim Higgins, she had occasion to pass behind one of the officers who was interrogating McBrearty.

"He [the officer] turned and showed her the half-sheet on which he had been writing", Higgins said. "There was writing on this sheet of paper covering approximately one-third of the page. There was the name of Frank McBrearty written in longhand at the end of this writing. She [Fowley] goes on to say that in front of the officer was a black and white photocopy of a manuscript signature of the name of Frank McBrearty.

"The garda officer showed her the half-sheet and asked her 'was it a good likeness?' She goes on to say, 'I took this to mean, were both signatures alike? I thought it was a practical joke. I started laughing and so did he'. She returned to her seat and the officer left the room with the papers on which he had been working. The garda [Fowley] took this to be a ruse and thought no more about it until recently when concerns about the veracity of the statement of admission obtained had been expressed in the media".

Fowley's statement made her the chief whistle-blower in the McBrearty affair, an absolutely key garda witness whose information pointed to a clear plot by gardai to frame particular individuals for the death of Richie Barron. Where once the claims of the McBreartys might have been easily dismissed by those in authority as the rantings of crackpots, they were now backed up comprehensively by a garda officer who had witnessed the very intimidation the McBreartys and others had complained about.

For her troubles, Fowley was shunned by her colleagues, although this was not the worst of it. In mid2002, Fowley, the key garda witness against An Garda Siochana in the Morris Tribunal investigating events in Donegal, was suspended from her job by garda management. She was reinstated only last year.

Tina Fowley is no angel. She was a junior officer during the framing of Frank Shortt and was criticised by the Court of Criminal Appeal for inventing evidence and for countersigning notes about meetings she did not attend. However, the court also pointed out that there was no allegation of perjury against her.

She was a slightly discoloured apple in a barrel of rotting fruit who redeemed herself greatly by coming forward in relation to what she saw happen to Frank McBrearty. Nevertheless, An Garda Siochana suspended her, greatly damaging her credibility as a Morris Tribunal witness.

John White was another garda whistle-blower, who saw wrongdoing against the McBreartys and, for whatever reason . . . perhaps it was an attempt to retrieve a reputation in danger of being destroyed by Judge Morris . . . pointed it out. Like Fowley, he too had questioned the reliability of the purported confession, arguing that it had clearly been concocted. He has also claimed that conversations between solicitors and their clients at Letterkenny garda station, which are supposed to be confidential, had been bugged.

White too was suspended by the garda authorities, who didn't stop there. Twice they tried to bring charges against him, firstly of perverting the course of justice and making false statements to gardai;

then of planting a gun on a travellers' encampment.

The determination of gardai to get a conviction against whistleblower White can perhaps be gauged by the fact that in the gun planting case, two assistant commissioners, two chief superintendents, three superintendents and several gardai of lower rank came into court to give evidence against him. And yet last Thursday, a jury took less than an hour to dismiss the charges. The previous charges didn't even get to the jury which was last year ordered by the trial judge to acquit White due to the unreliability of the chief witness, a man of very poor mental aptitude, who was subsequently given a three-year suspended sentence for making false statements."In my mind and in my opinion, I have been the subject of an ineffectual investigation", White said on Thursday. "There was no evidence in either case."

The failure of the gardai to bring successful charges against a whistleblower means that White's credibility, which was always in doubt when he had the court cases hanging over him, is now looking in slightly ruder health. Which might be important when he comes to give evidence to the Morris Tribunal in September in relation to the arrests of 12 people over Richie Barron's death.

It might also be of help if, as expected, Judge Morris criticises him in a report to be published very soon.

White's credibility also comes into play when assessing his claim that he had passed on "top class intelligence" to a senior garda officer 14 days before the Omagh bombing.

Thus far, the government has been able to dismiss the possibility that gardai knew about a plan to bomb Omagh but did nothing to stop it partly because White was not a credible character, but somebody with serious charges hanging over him.

That is no longer the case, and those claims by White suddenly look a little stronger. In many ways, his acquittal on Thursday was as big a blow for An Garda Siochana and the government as the Barr report.