A detective produced a firearm and placed it on a table in an interview room during questioning, the Morris tribunal heard yesterday.
The incident took place during the arrest of Mark McConnell (35) following the "silver bullet" allegation, a false claim that he had threatened a witness with a bullet in 1998.
Mr McConnell said that during his detention, the third time he was arrested in the years following the death of cattle dealer Richie Barron, Det Garda Matt Tolan produced his firearm during an interview.
"He came in, and he went to sit down, and he sat down, he got back up and he took the gun out of the back of his trousers, sat down again, placed it on the table." Mr McConnell said there was another garda in the room at the time, but he could not remember who it was. He said the weapon was "a small firearm, a revolver type gun".
Det Garda Tolan in a statement said that it would be "ludicrous" to produce a gun in an interview room because of the risk that a suspect might make a grab for it.
Mr McConnell, who was wrongly arrested after the Barron death in December 1996 and June 1997, also told the tribunal that detectives said his infant son, Dean, would be taken away and put in State care.