A 14-year-old schoolgirl was struck several times with a weapon as she lay on the floor in an area near the doorway of the room where her body was found, the Central Criminal Court has heard.
An expert in blood pattern analysis also told the court, Anastasia Kriégel's body was subsequently moved to another part of the room.
Two 14-year-old boys have denied murdering the teenager at a derelict house in Lucan in Dublin on 14 May 2018. One has also denied aggravated sexual assault.
John Hoade, an expert in DNA and blood pattern analysis at the Forensic Science Laboratory, told the court he visited Glenwood House on 18 May 2018, the day after Ana’s body was found.
He examined blood patterns on the walls and floor in the room where she was discovered and said the blood staining matched a DNA profile taken from the schoolgirl.
Mr Hoade told the court the patterns found in an area in the left-hand corner as one entered the room, indicated Ana was struck several times with a weapon as she lay on the floor in this area, that she lay in this position for a period of time after the assault and that her body was subsequently moved towards the back of the room.
He said there were patterns showing blood staining resulting from an object striking liquid blood as well as patterns showing blood, flung from a weapon.
The carpet in this area was saturated with blood.
Mr Hoade said the patterns showed the injured party's head was in contact with the wall just above the skirting board when she was struck on the head and that she bled into an area of the carpet just below.
He said he could not say how long she had lain in that area. But her body had moved or had been moved from that place to the area of the room where she was discovered.
Mr Hoade also told the court other blood patterns in the room indicated Ana had been assaulted at the back of the room, while she was upright.
He said a "swipe pattern" on the skirting board near the area of heavy blood staining indicated the schoolgirl had contact with this area while bleeding or an item wet with her blood had been in contact or wiped against it.
In all, Mr Hoade identified seven areas of blood staining in the room. He also examined a white stick found near her body and a concrete block found in the corner where the heaviest blood staining was identified.
Earlier, Detective Garda Gabriel Newton gave evidence that she received Boy A's clothing, boots and iPhone from his parents on 16 May.
Boy A had complained of being assaulted in the park on 14 May and Detective Garda Newton said she informed the parents that if the culprits were found they would need the clothing to check for evidence.
Boy A's mother told the garda that she had soaked her son's white top and washed it twice as there was blood on it. The garda was also asked if his black boots could be returned as soon as possible.
The clothes and boots as well as the phone were shown to the jury along with clothing received from Boy B and his parents.
The case will resume in the morning.