Manslaughter trial aborted after juror conducted 'home experiment'

A manslaughter trial involving a NSW police officer has been aborted due to the alleged misconduct of a juror, accused of conducting a "home experiment" on evidence presented.

Today a judge was forced to dismiss the jury during their deliberations following the three-week trial of Sergeant Matthew Kelly, who is accused of causing the death of motorcyclist Jack Roberts, 28, during a police pursuit at Blue Haven on the Central Coast in 2020.

The alleged misconduct came to light after the foreman wrote a note to a judge which explained a juror had used a 30-centimetre ruler, a book and their body to recreate evidence presented during the trial at the NSW District Court.

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By law, jurors must not conduct their own inquiries or discuss any evidence presented during a trial other than with fellow jurors in the jury room when all of them are present.

The note, read aloud in court, also explained that the juror recorded the results of his home experiment in a notepad and tried to present their "argument" to the jury, who refused to listen.

The letter went on to ask Judge Phillip Mahony if the juror in question could be dismissed, and allow the remaining jurors to deliberate, who would give an undertaking to ignore anything the rogue juror had presented.

Sergeant Kelly's defence barrister James Glissan, QC, made an application to discharge the jury and asked that the juror's conduct be referred to the Director of Public Prosecutions to consider whether charges should be laid.

The maximum penalty for jury misconduct is two years' jail.

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While Crown prosecutor Craig Everson, SC, argued the trial could continue following the dismissal of the one juror, Judge Mahony later dismissed the jury.

"Given that it goes to a central issue in the trial, namely causation (of Jack Roberts' death), viewed objectively it must give rise to a real risk of miscarriage of justice if this trial were to continue, even if an appropriate direction was given to the remaining jurors," Judge Mahony said.

Judge Mahony also asked for the alleged misconduct to be referred to the Office of the Sheriff of New South Wales to investigate whether the matter should be referred to NSW Police.

Sergeant Kelly is accused of hitting the back of Mr Robert's trail bike in his NSW Police car during a pursuit initiated after the 28-year-old was seen driving with no lights on.

He has pleaded not guilty to manslaughter due to criminal negligence and the alternative charge of driving dangerously occasioning death.

A new trial date is yet to be set.