`Border gardai aren't your ordinary gardai, because many of them feel they put their life on the line more often on the job, especially during the Troubles. It means discipline can be a problem and they can act like cowboys."

That is how one former garda attempts to explain a controversy in Donegal, upon which Garda Assistant Commissioner Kevin Carty will conclude work by the 24th of this month and submit a file to the Director of Public Prosecutions.

Mr Carty has conducted an investigation lasting almost a year into incidents, dating back to the mid-1990s, of alleged corrupt practices by gardai in Donegal.

Apart from his report to the DPP, an interim report will also be sent to the Garda Commissioner, Mr Pat Byrne, and the Minister for Justice, Mr O'Donoghue.

At a distance, the events involve a complex web of incidents and relationships, allegedly centring on a number of officers who cannot be named. However, at closer examination the affair, if proved true, is a shocking litany of abuse of power, with claims surfacing which may ultimately go beyond the Donegal Garda division.

One central strand of the allegations focuses on the death of Mr Richard Barron, a cattle dealer from Raphoe, Co Donegal, who was killed while walking home after a night's drinking in October 1996. It is claimed gardai were not on the scene for 45 minutes, even though the station is a short drive away.

Mr Barron, who died of head injuries, was taken in an ambulance but the scene was not preserved and it is believed the incident was treated as a hit-and-run traffic accident. The next morning locals swept the blood from the roadway and with it any forensic evidence that might have been there. A murder inquiry was opened nevertheless, and among those questioned were a local publican's son, Mr Frank McBrearty jnr, and his cousin, Mr Mark McConnell.

A second major strand of Mr Carty's investigation centres on allegations that some gardai in the district were dividing up caches of IRA explosives only to plant them subsequently, find them again and claim credit.

A garda has been suspended because of allegations made by his estranged wife on this matter. Another member has been transferred, and officially it is said this was a voluntary move. The wife, who has made a statement to the Carty team, has also implicated another Donegal woman, who it is understood has admitted that she transported the explosives along with hoax bombs to where they were then discovered.

It is also understood that diaries, purportedly kept by the suspended garda, have emerged detailing his alleged involvement. A spokesman for the estranged wife said this week that she stood by her allegations.

Mr Frank McBrearty snr (55) propped himself on a bar stool in his Parting Glass pub in Raphoe one afternoon this week, but would not comment about the explosives finds. He is guarded also about the fact that he and seven of his family have been interviewed regarding Mr Barron's death.

His pub and the adjoining Frankie's night-club are in the centre of the village. At the height of the club's success, buses ferried people from Derry and Strabane for a night out. Many of the locals felt the club brought in a rough element, and there were fights outside the premise.

There was also an incident between Mr McBrearty and Mr Barron dating back a number of years which is alleged to have occurred in Scotland. Members of the two families have come to blows since Mr Barron's death, but Mr McBrearty snr says he feels sorry for this family because they never found out how their father died.

"We always hoped for a breakthrough in the investigation. We hoped the truth of that man's death would come out. Even now, why don't they exhume the body? Isn't there DNA testing and all that nowadays? We're satisfied now that the State knows that we didn't do it and we're satisfied with ourselves, but justice has to be done," said Mr McBrearty.

Mr McBrearty cries when he tells of the effect of interrogations on seven of his immediate family and in-laws after they were arrested and questioned about the killing. He describes a confession to the killing allegedly signed by his son, dated December 1996, as "concocted evidence and lies, pure lies".

According to Mr McBrearty, this was followed by harassment in the form of flyers circulated around the village calling the family "the Murdering McBreartys". He claims there were a number of hoax bomb warnings and a series of threatening phone calls made to the family and their employees, one of which, phone records now show, was made from the home of a garda.

In the local District Court more than 170 summonses on public order and licensing offences are being contested by Mr McBrearty's legal team. The bulk are concerned with his bar and night-club over a seven-month period in 1997. Over the next few weeks and after the adjournment in the case requested by the DPP, Mr McBrearty's legal team says it will argue the summonses represented an abuse of process.

"The wider issues have not yet gone into evidence," says Peter Nolan, one of Mr McBrearty's legal team. "We have reserved our position on this and we await with interest the investigation's report."

Proceedings have also been issued on 15 related civil cases in the High Court, and Mr Nolan added that when the District Court proceedings had concluded these matters would be "vigorously pursued". A conservative estimate puts the total level of compensation that could be granted to the McBreartys in the High Court at around £5 million.

At the height of these alleged incidents the McBrearty family brought in a Meath-based private investigator, Mr Billy Flynn, who described arriving in Raphoe with his four investigators as arriving in the middle of an "Irish Vietnam. We were literally at war with local members of the [police] force".

He said his findings exonerate the McBreartys and he has written to the Carty team and the Department of Justice. However, Mr Flynn was convicted of the misuse of phone records as a result of his work on the case.

A garda memorandum, dated February 1998 and signed by a senior officer, states there was a campaign to discredit the gardai in the Donegal division, which was funded by Mr McBrearty and operated by Mr Flynn. In this memorandum officers are directed "to report any incidents or unusual contact that may occur either with Mr McBrearty and his extended family or Mr Flynn and his employees".

However, Mr Paudge Dorrians, a solicitor who represents two gardai questioned by the Carty investigation, stressed that the issuing of summonses to Mr McBrearty's family represented a "red herring". This was a separate matter and was not linked to the investigation of Mr Barron's death.

Mr Dorrians asserts that his clients were both involved in a second investigation into the death, which recommended that no charges be brought against the McBreartys and has claimed that these officers are now being made into "scapegoats".

It is understood that under questioning one of these officers made serious allegations against a senior member of the force.

"Members of the Garda who were involved in the second investigation into the death of Richie Barron pointed out in excess of 30 irregularities in the initial investigation and that these were not acted on. These members have been subjected to oppressive and unfair pressure and they are being publicly castigated by leaks emanating from presumed official sources," he said.

Both Mr McBrearty's legal team and representatives for the two gardai are seeking discovery of a statement made by a female officer based in Letterkenny. Both teams believe this statement will be beneficial to their case.

According to one local person, it's simply a case of bad cops being caught for their sins.

"If I go through the gap I'll bring a whole lot of you with me, it's a well known saying up here."

Whatever the truth, relations between some officers in Letterkenny Garda station, which is also the division headquarters, are said to be poor. "You could cut the atmosphere like a knife. Everyone is looking over their shoulder," said one garda.

Calls for a sworn public inquiry into the strands of the affair are getting louder by the day. Mr Jim Higgins, the Fine Gael spokesman on justice, took an early interest in the case and has said a public inquiry is the only way to access the full truth.

"I have to accept the Minister's word that there is an ongoing, thorough investigation and this team should be allowed to do its work, but the investigation can't take evidence under oath and that is what's needed," he said.