Gardaí were on Friday night questioned a man on suspicion of involvement in the murder of Derek Coakley Hutch in Dublin last year.
Coakley-Hutch, a 27-year-old father of two, was a nephew of the veteran Dublin criminal Gerry Hutch, also known as The Monk.
He was shot dead at Bridgeview Halting Site, Cloverhill Road, Clondalkin, Dublin 22 on January 20th, 2018.
Coakley-Hutch was throwing drugs over the wall of the prison into an associate in the jail exercise yard when he was shot as part of the Kinahan-Hutch feud.
The man being questioned was being held at Ronanstown Garda station in west Dublin under Section 50 of the Criminal Justice Act.
The suspect is in his 20s and is from north Dublin and can be held for up to seven days without charge
Gardaí suspect he may have aided the gunman who carried out the murder. He is the third person arrested in connection with the fatal shooting though the killing remains unsolved.