Murder jury 'distracted by post-G20 alarm'

An ex-soldier convicted of murdering a Gold Coast nightclub singer should be acquitted because an alarm distracted the jury at a critical moment during his trial, a court has heard.

Matthew Cox was given a life sentence after he was found guilty of bashing Tony Williams to death with a hammer at his Mermaid Waters apartment in December 2011.

But at a Court of Appeal hearing on Tuesday, barrister Carl Heaton QC argued the trial had been marred by an alarm sounding in the building during the judge's directions about the defence of provocation.

During the trial, the defence team had argued Mr Williams' fatal injuries were inflicted in self-defence during a confrontation.

But the jury instead accepted the Crown's case that Cox was jealous of the effect the Sex `N' Chocolate singer had on his girlfriend and attacked him in a premeditated act.

Mr Heaton noted the provocation defence was a crucial aspect of the defence case and said while the trial judge paused at times, he didn't stop delivering directions as the alarm sounded.

That all took place not long after Brisbane hosted the G20 summit in November 2014, he added, alluding to security fears at the time.

"The world is certainly more acutely aware of security and of safety (and) the events of the G20 only stood to heighten that sense of community concern," he told the hearing.

"The period when the alarm was sounding almost entirely covered the period during which the directions on provocation were given to the jury."

He also argued some evidence heard by the jury from Cox's girlfriend "polluted" and prejudiced their opinion.

Justice Martin Flanagan queried the alarm argument, noting there was no evidence of the instructing solicitor observing any signs of distraction among the jurors.

The three judges on the bench reserved their decision.