A senior garda today denied putting a gun in an electrician's mouth and spitting in his food.
Retired detective garda Sean Herraghty told the Morris Tribunal Damien McDaid had fabricated stories and later identified him so he could stick the allegations against someone.
Mr Herraghty said a possible witness in a prosecution against others it was important to bring Mr McDaid on side rather than alienate him with abuse.
Mr McDaid claims he was assaulted in Letterkenny Garda Station in December 1996 by officers investigating the death of hit-and-run victim cattle dealer Richie Barron, who gardai wrongly believed had been murdered.
The 41-year-old had previously pointed out Mr Herraghty as the officer who ordered him to his knees in the middle of an interview and had put a gun in his mouth.
"It's completely untrue," said Mr Herraghty. "That to me would be a very criminal act to perpetrate against anybody. That's something like you'd hear coming out of west Belfast or somewhere like that.
"That doesn't happen in a civilised society. There's no way I would be involved with the misuse of a firearm in any stage of my career."
Speaking in the public gallery, Mr McDaid shouted: "Do you think putting a gun down my throat was a figment of my imagination? You're joking me."
The prisoner also claims the garda spat in his breakfast and jumped up and down on his feet.
"I can say it didn't happen," continued Mr Herraghty. "I never spat at anybody or in their food in my life. These allegations are very serious. None of that happened.
"The gun incident is a very, very serious manner, the spitting in his food a despicable act. I can assure you I never jumped on a prisoner in my life.
"If he had been abused in custody he would have been a hostile witness in the event of a prosecution."
Mr McDaid, who cannot read or write, was arrested as an accessory after the fact of murder. Gardai accused him of seeing suspect Frank McBrearty Jnr with an iron bar the night Mr Barron died and hiding the weapon for him.
Four years later, while serving a prison sentence for unconnected offences, Mr McDaid was visited by two gardai who he claims promised that if he were to make a statement that Mr McBrearty Jnr had an iron bar or asked him to conceal it they would ensure his release.
The tribunal also heard Mr McDaid believed he was victimised by gardai in Donegal following the investigation.