Accused killer was jealous: psychiatrist

A man accused of stabbing his girlfriend to death probably did so because he was jealous about her infidelity and has a borderline personality disorder, a forensic psychiatrist says.

Michael James Quinn, 27, is on trial in the Sydney Supreme Court for the murder of Cherie Vize, who died of a knife wound to the neck at his Wollongong home in July 2013.

"We are talking about someone who is clearly in a highly disturbed state of some type," Dr Richard Furst told the court on Wednesday.