Australians all want to know: How did Lisa Harnum die?

'Insanely jealous' boyfriend denies throwing his girlfriend from 15th-floor apartment balcony

Lisa Harnum's death is being investigated (Rex)

"Help me! God help me!" A minute after screaming those words, Lisa Harnum plummeted to her death from the balcony of a 15th-floor luxury Sydney apartment. But did the former ballerina fall – or was she thrown by her boyfriend, a man so "insanely jealous" he bought a computer programme to spy on her text messages and installed hidden cameras in their home?

For the past month, Australians have been gripped by Simon Gittany's murder trial, unfolding in the New South Wales Supreme Court. The clean-cut 40-year-old – accompanied to court every day by a stunning brunette the spitting image of his dead ex – does not deny being "controlling, intimidating [and] abusive". But he rejects the accusation that he killed Ms Harnum in "a fit of apoplectic rage" in July 2011 after finding out she was planning to leave him.

Last week, state prosecutors wrapped up their case, after painting a picture of a man who sought to control every aspect of Canadian-born Ms Harnum's life. Mr Gittany forced her to quit her hairdressing job, the court heard, alienated her from her friends, and allowed her to leave their flat only to buy groceries. He also instructed her never to look at another man, since "your eyes should only gaze on me, the one", he told her.

A pinhole camera which he installed in the corridor outside their flat, in an upmarket city centre block, recorded a struggle during which Ms Harnum hammered on a neighbour's door, screaming for help. Mr Gittany then dragged her back inside, hand over her mouth. Soon afterwards, the neighbour heard "a single, bone-chilling scream" – and a passer-by saw a man "unload" a black object off the balcony.

The defendant told the judge-only trial that the 30-year-old Ms Harnum climbed over the balcony after he told her to pack her bags following a row. She fell on to the awning of the apartment below, he said, and as he leant over, trying desperately to grab her and haul her back to safety, she lost her footing and fell. "I screamed out her name in despair," he recalled.

On trial: Simon Gittany and his current girlfriend (Rex)

A succession of witnesses told Justice Lucy McCallum about a relationship that Mr Gittany agreed was "dysfunctional". According to Ms Harnum's mother, Joan, who travelled from Canada for the trial, the defendant would make her daughter kneel in front of him and "swear she would do as she was told".

In their last phone call, the day before she died, Ms Harnum confided in her mother that she was "very afraid", and begged her to "come over and help me", the court heard.

It also heard testimony from Ms Harnum's personal trainer, Lisa Brown, whom Gittany hired to train with her at their home, because he feared that men would look at her in the gym.

Ms Harnum confided in her counsellor, Michelle Redmond, that the relationship had reduced her to "a mere shell of a person", isolated and friendless. Ms Redmond claimed that Mr Gittany, who had found out she was helping his girlfriend to move out her possessions, phoned her a few days before Ms Harnum's death and warned her never to contact her again.

Mr Gittany depicted his ex as a vulnerable woman who on several occasions had "jumped out of moving cars", and once ran into the middle of a traffic-choked Sydney street. After one such incident, he said, she told him: "When I'm upset, I genuinely don't know what I'm doing."

The senior Crown prosecutor, Mark Tedeschi QC, cast doubt on his version of events, noting that Ms Harnum had left no fingerprints on the balcony, and that she was clutching her handbag when she died.

The defendant had conducted "the most intense surveillance of his partner that one could possibly imagine," Mr Tedeschi told the court, adding: "He was not satisfied with her having even the tiniest part of her life that he didn't know about or control."

Mr Gittany admitted installing the secret cameras, to keep an eye on tradesmen and his cleaner. A verdict is expected in the next fortnight.