A woman has tearfully recalled the last phone call she had with her daughter, the day before she was allegedly thrown to her death by her fiancé.

Simon Gittany is standing trial for the murder of Lisa Harnum, accused of lifting her over a 15th floor balcony railing and letting go, during an argument in July 2011.

He has pleaded not guilty to murder and says his fiancee climbed over the balcony railing herself.

Lisa's mother Joan Harnum told the court, the day before she died, her daughter made her promise to contact her psychologist if anything happened to her.

Mrs Harnum said she had been asked to come and collect her daughter, so they could return to Canada together.

The next day she was informed of her daughter's death by a Canadian police officer.

Mrs Harnum said she told her 30-year-old daughter that if things got really bad she should just grab her passport and purse and get out.

The trial has heard Simon Gittany had prevented Ms Harnum from leaving him days before she died.

The Crown alleges he was extremely possessive and controlling to the point where she lost her friends and regular contact with her family in Canada.

The Supreme Court in Darlinghurst heard Gittany tracked Ms Harnum's movements, text messages, emails and phone calls and had cameras set up in their apartment.

The Crown alleges that just days before she died, Ms Harnum knocked on her neighbour's door begging for help and was then dragged into their apartment by the accused.

Gittany's lawyer Philip Strickland, SC, argues Ms Harnum went over the railing of their balcony and Gittany tried to help her, but she fell to her death.

He told the court although her motive for going over the balcony was unknown, it may have been suicide or a cry for attention.

The defence argues that she was conflicted and confused and suffered from low self-esteem.