A BRUTAL gangland thug was spared even more jail time after he admitted his role in a savage assault on a criminal who became a supergrass in a high profile murder trial. Crumlin gangster Ian 'Mad Dog' Maloney (25) repeatedly kicked Joey O'Brien in the head as he lay semi-conscious in Charlie's Restaurant, Dame Street, on January 4, 2009. sickening Maloney -- who was connected to 'Fat' Freddie Thompson's mob -- is currently serving a 12-year sentence for the €1.2m armed robbery of Paul Sheeran Jewellers in Dundrum Town Centre on September 3, 2008. Just four months after that robbery he subjected Joey O'Brien -- the State's 'star witness' in a murder trial last summer -- to a beating which a judge yesterday described as "sickening". Self-confessed Crumlin drug dealer O'Brien -- who is now in the witness protection programme -- gave the key testimony that helped secure the conviction of gangland killer Peter Kenny (30), from Rialto, for the savage murder of Johnny 'Champagne' Carroll in February, 2009. A source explained: "A lot of people want O'Brien dead -- there is a contract on his head. "Mad Dog hated him because he used to bully him when he was a young fella -- he was delighted to get a chance to batter him. "The beating that O'Brien got was very severe -- Maloney was calling him a rat as he danced on his head." Yesterday, Dublin Circuit Court heard O'Brien woke up the next morning in hospital with a broken jaw, smashed teeth and a broken eye socket. He was badly concussed and could not remember much about the attack. Pieter Le Vert, defending Maloney, submitted that his client has offered a full apology. He said Maloney's brother had died several years ago shortly after been released from garda custody and he blames the authorities for this. He said this led to his client starting to drink and use drugs before becoming involved in crime. Mr Le Vert said Maloney is now drug free and the recent birth of his son has "changed him entirely". Judge Nolan called it a "sickening assault" and said it appears Maloney inflicted most of the injuries. assault However, he said there is some hope he will reform and that he would not extend his prison term. He sentenced Maloney to four years to run alongside his current sentence. Mad Dog's friend, Jonathon Murray (22), was jailed for 18 months for his role in the assault. The court heard that Maloney has 73 previous convictions and Murray has 48, including four for drug dealing.