The trial of a 17-year-old boy who is charged with the false imprisonment of former tánaiste Joan Burton in November 2014 has heard it was like a "rugby maul" as they tried to move Ms Burton from one garda vehicle to another.

Detective Inspector Derek Maguire was giving evidence on the second day of the trial at the Children's Court.

The prosecution alleges the boy was involved in trapping Ms Burton and her adviser Karen O'Connell in two garda vehicles for two to three hours, without their consent, as they left a function in Jobstown in Tallaght.

The boy has denied the charges.

Inspector Maguire said a small group had gathered as Ms Burton attended a graduation function at An Cosán in Tallaght.

As she moved from the centre to St Thomas’ Church for the conferring ceremony, a group of protesters converged on her shouting abusive comments and calling her names.

Objects including water balloons were also thrown, he said.

He said they were forced to stop a number of times while walking towards the church and while she was in the church the crowd outside began to grow.

It was decided Ms Burton should leave the area in an unmarked garda car as it would not be safe for her to return to her own car.

He said the atmosphere was one of "pure aggression".

Inspector Maguire said it had been decided that Ms Burton should leave the area but they were prevented from leaving when protesters surrounded the car as it attempted to leave the church.

He said he was becoming concerned for the safety of the then-tánaiste and her adviser as protesters started to shake the car while shouting profanities and blocking the windows of the car with placards.

He said he tried to speak to one of the people he recognised and whom he believed was orchestrating the protest but he refused to speak to him.

He called Command and Control for more assistance as he became concerned about the growing number of protesters.

The defendant, who was 15 at the time, was among those at the front of the garda car in which Ms Burton was sitting and was using a Loud Hailer and taking mobile phone footage, the inspector said.

He said the defendant "seemed to have his phone out a lot and was pointing it quite close to our faces". He did not know the defendant at the time and he was later identified to him.

Inspector Maguire said after some time it was decided to form a human cordon on both sides of the former tánaiste and try to get her to a garda Jeep.

He said it took seven to ten minutes to move 30 yards between the two cars because protesters had converged on them.

He said at this stage the protesters were showing "pure aggression" and there was  a lot of "vitriol, very aggressive tension in the air and a very uneasy feeling."

He said the protesters were asked a number of times to leave the area under the Public Order Act but they refused to do so.

The court heard that after Ms Burton was moved to a garda Jeep protesters began a slow march in front of it. The protesters then stopped again and the Jeep could not move, he said.

The public order unit had arrived to assist and some negotiation took place resulting in this unit being moved to the side allowing a slow march to resume.

Inspector Maguire said Ms Burton had left the church at 12.30pm and by 3.45pm she had only moved 300 yards.

The trial continues at the Children's Court.