One of the boys accused of the murder of 14-year-old Anastasia Kriégel asked gardaí if they were joking him when told her blood had been found on his boots.
The boy also denied being in the room where her body was found.
Two 14-year-old boys deny murdering the schoolgirl in a derelict house in Lucan on 14 May last year. The first accused boy also denies aggravated sexual assault.
The jury watched part of the first interview conducted by gardaí with the then 13-year-old accused boy, after his arrest for the murder of Ana on 24 May last year.
Boy A, wearing jeans and a hoody, nodded as gardaí told him he had been arrested on suspicion of murder and explained to him that he did not have to answer questions unless he wanted to.
He was also asked if he understood the difference between right and wrong and between truth and lies.
Garda Tomás Doyle gave evidence of conducting the interviews with the boy along with his colleague Garda Marcus Roantree.
In the third interview on the same day, the gardaí showed the boy a photograph of the black boots he had been wearing on the day Ana went missing and told him Ana's blood was on the boots.
Boy A asked the gardaí "are you joking me?" and asked them if they were actually being serious.
Gardaí replied that they would not joke about it and the boy asked if it was OK if he got air and asked for water.
Told by gardaí that this was significant and serious, Boy A replied that he was aware.
Garda Doyle told the court that he showed Boy A various clips of CCTV footage from the day Ana went missing, during the interviews.
The boy said a male in St Catherine's Park, dressed in black and wearing gloves might be "one of the lads" who had attacked him in the park on that day.
Gardaí informed him they believed he was actually the person in this clip and in several other clips.
The boy was told a backpack had been found during a search of his house and he was shown a photograph.
He said he did not have the backpack with him at any stage in the park on the day and denied that footage of a boy wearing a bandage on his right hand and carrying a backpack was him.
Shown a picture of a type of builder's tape, he said he had never had such tape in his possession.
Gardaí told the boy that the Garda Technical Bureau had been through the room in the derelict house in which Ana was found "with a fine toothcomb".
They said Ana had been murdered in the room, and her blood was on his boots and asked if there was anything he could tell them to establish the truth of what happened to her.
The boy replied there was nothing else.
Gardaí put it to him the only place he could have got her blood on his boots was in the room where her body was found.
The boy denied being in the room on the day she went missing.
He told them that a previous witness statement in which he said Ana had stormed off in the park and he was later attacked by two men, was the truth.
The trial will continue tomorrow.