A semen sample matching that of a book-keeper accused of murdering his wife was found on a bedsheet near the victim's body, the Central Criminal Court has been told.
A forensics expert said yesterday the DNA extracted from the sample also matched one in every 200 Irish people.
Ms Joy Peden, of the Northern Ireland Forensic Science Agency, said the DNA of the victim, Ms Miriam O'Donohoe, was mixed with the semen sample matching her husband.
It was the 12th day of the trial of Mr Paul O'Donohoe (44), of Aberdeen Street, Dublin, who denies the murder or manslaughter of his 42-year-old estranged wife, Miriam, at her home in Ashfield Gardens, Mulhuddart, on January 25th, 1997.
Prosecutors allege that Mr O'Donohoe murdered Ms O'Donohoe and then threw objects around her house to make it look as if a burglar had killed her.
Det Supt Derek Byrne told the court that, after the killing, he had 15-20 meetings with Ms Debra O'Connell, a friend of Mr O'Donohoe.
She told him that Mr O'Donohoe had confessed to her. He agreed that he had not disclosed to the DPP and to Mr O'Donohoe's defence team that he had had these meetings with Ms O'Connell.
The trial continues.