The Central Criminal Court has heard that Jean Gilbert, who was stabbed to death at her Dublin home, had been writing to a man in England for some months before her death.
Her husband David Bourke denies his wife's murder in Castleknock in August 2007.
Jean Gilbert's brother Robert told the court that Mr Bourke turned up at his parents' house early one morning, two months before Ms Gilbert died.
He said Mr Bourke told him that Jean had said she wanted to separate.
Mr Gilbert told the court that up to that point he was not aware of any problems in his sister's marriage.
However, he said he learned that she had begun communicating, by letter, with a man in England in the early part of that year.
He said from that time he stayed in regular contact with his sister and was called to the hospital to identify her body on the day she died.
State Pathologist Dr Marie Cassidy said Ms Gilbert had suffered four stab wounds to the body and several other injuries to her hands.
Garda witnesses gave evidence of interviews conducted with Mr Bourke at Blanchardstown Garda Station.
The court heard that the accused man told gardaí that he wanted to hurt his wife, but not to kill her.
In the interviews he also told detectives that he was sorry for the pain and suffering caused to his children.
