A boy told a detective that he believed his colleague was injured.
The defendant claimed that he had suffered injuries from female student Anna Krieger in the attack of two older teenagers, and the trial heard.
Detective Garda Marcus Roantree told the Central Criminal Court that he had arranged to trace the last interaction between Boy B and Anna.
When Gda Roantree met with Boy B on May 17, 2018, Anna's body was just discovered.
Gda Roantree said the boy B told him that he heard that Anna's body was found and he was nervous because he was one of the last people to be with her.
Gda Roantree also provided evidence that Boy B told him boy A that his mother called his home on May 15, the first time he had learned that boy A was attacked.
Boy B said Boy A had spoken briefly.
Boy B told Gda Roantree that he believed "Anna did it to him" because there would be more marks on Boy A's face if he was attacked by two big men.
Gda Roantree also told the jury that he voluntarily collected DNA samples from Boy a on May 16, 2018 and took photos of his alleged injuries during the attack.
Gda Roantree said that boy A told him that Anna touched him and put his hand on his shoulder and chest, which might help.
Gda Roantree told prosecutor Brendan Grehan SC that he did not ask the boy any questions and when he said Ana, garda knew he was referring to Ana Kriegel, who is still missing
The Central Criminal Court also heard that boy A helped gardai produce computer images of two older men he claimed attacked on the day Ana went missing.
Detective Garda Mairead Crowley said she spent three and a half hours with boy a making evofit or computer images of two people he said attacked him in the park.
Gda Crowley said that on May 17, 2018, Boy A and his mother came to Garda headquarters to complete the computer drawing.
Gda Crowley said boy A made A "very good description" of both of his attackers ".
In their evidence, the mother of boy A said that when he came home around six o'clock P. M. in the evening, her son looked "very, very pale and trembling ".
His father said Boy A looked dirty and dusty.
He told him that he was "jumped" by two older young men.
His father also said that boy A told him that he was in the park with Boy B but did not mention Anna.
Earlier, Gda Seamus Timmins said he checked CCTV footage from the park between 4.
At eight o'clock P. M. on May 14, 2018 and he did not see any evidence that boy A was accused of being the attacker.
However, he did not accept that all the cameras in the park were working.
In this afternoon's evidence, the father of boy A said that his son was "shaking" when he spoke to him in the bedroom around six o'clock P. M. and had A little blood on his lips.
He said his son limped and his hands were dirty.
He told him that he was "jumped" by two older young men in the park.
The father of boy A said he had A cup of sweet tea for his son.
The couple then drove around the park to see if they could find anyone who met the description given to him by his son, but no one met the exact description.
In her evidence, the mother of boy A said that her son had been allowed to go out and that he would go home at around six o'clock P. M.
He called her to the bedroom.
He was "very, very pale and trembling," she said ".
She said he looked flustered and trembling.
Her son has a small piece of blood on his T-shirt.
The shirt and a small amount on his bottom pants.
She said he looked like he was "beaten" and told his parents that he was attacked by two young people in the park.
She told the court that she later washed her son's clothes.
In cross-examination, the mother of boy A admitted that she did not remember the exact time when her son told her that he had met Boy B in the park.
Earlier park administrator Norman Macon told the Central Criminal Court that he noticed a little blood on his finger, and that a teenager's face and trousers told him that he had "hidden a little" in the woods ".
Mr. Macon said he had spoken to the boy who looked "about 16 years old" because his father knocked at the door and complained that his son had been attacked.
He said the man was "very angry" and told him that his son was "jumped" in the woods by "a few big guys.
Mr Macon asked the man if he had contacted galdai, who said he had been working hard but could not reach them.
Mr. Macon called garda radio and when the call was answered, he handed the call to the man.
The man's car was parked near the ranger station.
Mr. Macon said that he could see a shadow in it. he thought it was his son, so he went to the car.
He "just meddled" and wanted to see if the boy needed help.
When Mr Grahan asked him what he saw, Mr McCann said he saw a young man in a white T-shirtshirt.
His hair was "everywhere" and looked like a fight.
Mr. Macon said he asked the boy what had happened and whether he was OK.
The boy put his hand on his eyes and told him "just hid it in the woods for a while ".
Mr. Macon said the boy did not seem to want to associate with him.
The court heard his hand shaking.
Mr. Macon said that he did not look too carefully, but he noticed that there was "a little bit of blood" on the boy's fingers ".
He also had a little blood on his trousers and a little bit on his face ".
When asked about the boy's manners, Mr. McKenzie said the young man looked "like a rabbit caught by the headlights ".
Earlier, a doctor who examined Boy a said he suffered "soft tissue injuries consistent with blunt trauma ".
The GP examined Boy A's mother after taking him to the clinic on May 16, 2018, as he was injured in the alleged attack two days ago.
The evidence provided by the GP suggests that boy A told him that he was attacked in A random attack at about 5. 30pm on May 14.
Boy A told the doctor that he was caught from behind and taken to the ground, and two young men kicked and punched.
The doctor said the boy A told him that his right knee, lower back and chest had been kicked.
The general practitioner told the Central Criminal Court that he had a brief examination and found that there was bruises and tenderness in the lower part of the back of Boy a and swelling in his right knee.
The teenager also had pain in his right wrist.
The doctor said that boy A suffered soft tissue injury consistent with blunt trauma.
Several parts of his body showed signs of injury, including his knees, chest and wrist.
The 13-year-old pleaded not guilty to Ana's murder (14)
On May 14, Glenwood building in Laraghcon, Clonee Road, Lucan.
One of the boys, A, also denied allegations of serious sexual assault.
Three days after Anna's disappearance, gardai found her naked in an abandoned farmhouse.
The last time she was seen leaving home with Boy B at five o'clock P. M. on the day of her disappearance.
The prosecution case was when Boy B "lured" Anna to an abandoned farmhouse and then watched another boy sexually assaulted and murdered her.
The trial continues.