A youth ran after a garda who was chasing his friend shouting: "I'm going to smash your face in if you don't let him go."
Shane O'Shea (19) followed a garda into a shopping centre with his fists clenched, shouting: "I'm going to get him."
He claimed he was just going to get his friend after they had been kicked out of McDonald's restaurant for drinking, shouting and being abusive to staff and diners.
A judge sentenced O'Shea to five months in prison, saying he acted as if the court was a TV show. The accused was laughing down at his friends, who were later removed from the court for causing a disturbance.
Judge Cormac Dunne said O'Shea acted like it was normal to be before the court. But it was not normal -- that of the 4.5 million people in Ireland only about 20,000 regularly come before the courts.
"Why do you act the thug," asked Judge Dunne. "It's not normal to get plastered drunk and go out and disturb the diners, with their children, who are having a meal."
O'Shea, with an address at Grove Road, Harold's Cross, appeared before Dublin District Court charged with threatening and abusive behaviour and failing to follow the directions of a garda. He had denied the charges.
The incident took place in the Swan Shopping Centre, Rathmines, shortly before 7pm on October 12.
Garda Michael Connolly said he was called by staff to McDonald's restaurant after they complained that a group of youths were being verbally abusive and hassling customers.
Garda Connolly said the youths were drinking alcopops and shouting abuse at staff and customers. The court heard the youths were directed to leave McDonalds, which they eventually did, but remained standing outside the restaurant.
They were told to move again, which they refused to do. A second youth tried to evade arrest and ran away.
Garda Connolly said Garda O'Toole chased after this youth, and O'Shea followed him, shouting: "I'm going to get him."
In his evidence, Garda O'Toole said O'Shea came up behind him, with his fists clenched, and said: "I'm going to smash your face in if you don't let him go."