David Bagster, 54, pleaded not guilty in the Wollongong District Court to the manslaughter of Ms Birch, who was found hog-tied and upside-down in the bin on March 22, 2011.

He was accused of unlawfully killing his 34-year-old partner after a nine-month relationship marred by domestic violence.

Read more about the trial:

Jurors deliberated for more than three days before telling Judge Andrew Haesler on Thursday that they were unable to come to a unanimous verdict, following a trial that ran for three weeks.

They were asked if they could reach a majority verdict - that is, 11 to 1 - but after a short period of consideration, they said this was not a prospect either.

Judge Haesler said the jurors had carefully adhered to the evidence, and there was a danger that if they were kept to deliberate longer and did reach a verdict, some jurors might not abide by their oath.

He commended the jurors for their efforts before discharging them.

The Director of Public Prosecutions will now review the matter and determine whether Bagster will face retrial.

The court heard from several witnesses during the trial who spoke of witnessing aggression from Bagster, directed at Ms Birch.

But Bagster's defence counsel Scott Fraser told the jury that witnesses were lying because they did not like his client.

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