The Ana Kriegel trial has heard a DNA sample taken from her top matched the DNA profile of one of two teenage boys on trial for her murder.
The 14-year-old schoolgirl's body was found in a derelict farmhouse in Dublin on May 17th last year - three days after she was reported missing by her mother.
It is the prosecution's case that Boy B lured Ana from her home in Leixlip on May 14th last, knowing what was to happen to her.
He denies her murder.
Boy A is accused of violently sexually assaulting and murdering the schoolgirl.
He has pleaded not guilty to both charges.
Today, the jury has been listening to the evidence of Marce Lee-Gorman from Forensic Science Ireland (FSI), who was asked to examine Ana's clothes.
She said she found semen staining on two areas of a black vest top that was found in the same room where Ana's body was found in a derelict farmhouse in Lucan three days after she went missing.
She said the mixed DNA profile generated from the stains matched Ana and Boy A's reference samples.
She also said she was of the opinion that force was required to cause the extensive damage she observed to her top and bra.
Reporting by Frank Greaney