One of the teenage boys accused of murdering Ana Kriegel asked a Garda detective if he "was joking" when he told him the blood of the 14-year-old girl had been found on his boots.
The accused also denied he was in the room where the schoolgirl's body was found, the Central Criminal Court heard.
Ana's body was found in a derelict farmhouse in Lucan, Co Dublin, on May 17 last year.
Boy A was arrested over her murder a week later.
Barrister Gerardine Small, prosecuting, led Detective Garda Tomas Doyle through the interviews carried out on May 24.
During questioning, Boy A said he was in the company of Ana on May 14, but when Detective Doyle told him that Ana's parents reported her missing at 8pm, he denied being with her in the period leading up to that time.
Detective Doyle showed Boy A a picture of the boots he had been wearing that day and told him blood analysis showed Ana's blood was on both boots.
The court heard that Boy A responded: "Are you joking me? Are you actually being serious?"
Detective Doyle said he told him that he would not joke about the matter.
Boy A then asked if he could "get air" and asked for a glass of water.
Detective Doyle told the suspect the case was "significant and serious", to which Boy A replied: "I am aware."
Two 14-year-old boys, who cannot be identified due to their age, are standing trial accused of Ana's murder.
Boy A has pleaded not guilty to murder and sexual assault "involving serious violence" of the schoolgirl.
Boy B has pleaded not guilty to murder.
Boy A previously claimed that on the day Ana disappeared he was attacked by two men in the local park where he had last seen her. He also retraced the route he said he had taken with Ana to gardai.
During the Garda interview on May 24, Boy A was shown CCTV images taken the day she disappeared and was asked about two males in the video.
He told gardaí that it looked like "the lads" who beat him up.
"That might be good news. I think it's one of the males who beat me up. Is there any more footage?" he said.
Gardaí told Boy A they believed it was him in the footage.
"We believe that is you in the footage and it shows that the route you told gardaí was not correct," the detective said.
Boy A denied he was in the footage before being asked if he could tell gardaí anything to help their investigation.
"No. There is nothing else," the accused replied.
Detective Doyle added: "What I'm saying to you is the only place you could have got blood on your boots was by being in that room. Were you in that room?"
Boy A denied he was in the room where Ana's body was discovered.
He was then asked if the statement he provided to gardaí when Ana was still a missing person was the truth, to which he said it was.
Following Boy A's arrest, gardaí searched his home and found a backpack in a wardrobe. Boy A was shown a picture of the backpack and asked if he had had it with him on the day Ana disappeared.
He said he didn't and that he never had his backpack in the park.
He also told gardaí that he liked to draw and that he was good at drawing pictures of the anatomy.
He expressed an interest in drawing the inner anatomy, like a skeleton.
