When former Liberal staffer Bruce Lehrmann's prosecution for alleged rape was abandoned by the ACT government in 2022, it put juror misconduct in the spotlight.

The ACT Supreme Court case ended in a mistrial after a juror brought a research paper into the jury room. The territory has since ramped up its laws — and the punishment for jurors who misbehave — in response.

But it wasn't the first time juror behaviour had hit headlines.

Serious juror misconduct has jeopardised trials in courts across the country. Why is it happening — and how are the courts responding?

What is juror misbehaviour?

Queensland barrister Jeffrey Hunter KC says there's a dearth of data in Australia about juror misconduct, including how often it happens.

Nonetheless, it's clear that it is a recurrent problem, based on the instances that are publicised and recorded.

Those instances include a WA juror posting on Facebook on day one of a murder trial, "At Perth District Court, guilty!" before being dismissed by the judge, or the notorious Sydney murder trial that was aborted after "rogue" jurors planned a visit to The Gap, the site of the alleged crime.

Earlier this year, another WA juror was found to be in contempt of court after sharing information about a rape trial with a friend.

Sheriff of New South Wales Tracey Hall, who is responsible for jury service administration in her state, calls it "a very sad example of a breach of the sanctity of a jury deliberation room".

In a chat group with five friends, the juror talked about the case and named the complainant. Without telling the juror, one of the friends contacted the complainant via social media and phone messages.

"He had information that he wasn't entitled to have," Ms Hall tells ABC Radio National's Law Report.

The friend told the alleged victim that the jury didn't believe her evidence and that she was wasting taxpayer money. He later pled guilty to stalking and was fined $8,000.

The juror was charged with two counts of contempt of court and fined almost $15,000.

The UK, in contrast to Australia, has conducted major research into juror behaviour, including a UK Ministry of Justice study involving over 600 jurors.

"[That] showed that, at least in 2010, a really quite significant proportion of juries, but especially in high-profile trials, were doing the wrong thing," Mr Hunter says.

"There's no reason to think that Australian juries are behaving any differently from those in the United Kingdom."

'No shades of grey'

When jurors enter the jury system they're given induction training, which covers all the things they cannot do as a juror and their legal responsibilities.

"It is very clear," Ms Hall says.

For example, a juror is told they can't mention the case on social media, or talk about the case to other people.

Nor can they do their own investigating, for example, by going to view the scene of the event in question, or by researching law or facts about a trial before the verdict.

"It's never acceptable, and there are no shades of grey around this," Ms Hall says.

Yet, it continues to happen.

She cites another recent example of a trial involving a car driven by a police officer. A juror with a background in mathematics independently measured the ground clearance on a similar make of car, to reach his own conclusion about what happened.

"He believed he knew better than the evidence that had been provided by the court," Ms Hall says.

The juror was fined $1,100.

In another example, from June this year, during a six-month tax fraud trial in the NSW Supreme Court, the Australian Federal Police (AFP) informed Ms Hall they had seized the phone of a person who happened to be a jury member of the trial. The AFP's enquiry was unrelated.

They'd found that the juror had made prohibited internet searches on his phone relating to the trial and to the accused.

"But also there were text messages of him discussing selling illegal drugs to another juror," Ms Hall says.

The trial judge discharged both jurors, and their charges are yet to be handed down.

The trial was in its 74th day and, fortunately, the rest of the jury was able to proceed to deliberation and a verdict, because 14 jurors had been empanelled, even though only 12 were required.

In NSW, a recent legal amendment allowed additional jurors to be empanelled in cases so that, in the event of juror illness or issues like juror misconduct, a juror can be discharged and there's still a valid jury left for deliberation.

There is also provision for a trial to continue with a reduced number of jurors in Victoria, New South Wales, Queensland, Western Australia (for civil trials only), South Australia, Tasmania and the ACT.

Tackling 'natural curiosity'

In 2008, a UK juror posted a Facebook poll to elicit her friends' advice about whether to vote guilty or not.

But Mr Hunter says juror misconduct of that kind isn't the norm.

"I think we can safely say that sort of stupidity is rare.

"It's far more common for jurors to wonder what [they] can find out about this [trial]," he says.

"People are naturally curious. And if you haven't heard about something, if you hear about something for the first time, well, you don't want to wait till the expert gives evidence in what might be days' or weeks' time. You want to find out about it now, on the bus when you're on your way home."

That's a tricky problem, and increasing penalties isn't necessarily the answer.

"A lot of our jurors tend to be people who have retired and I'm not sure that everyone would be comfortable with the idea of imprisoning them," Mr Hunter says.

"But, that said, in the UK, the response is unsparing. The principle over there is that abuse by a juror of the internet is always a serious matter, and usually, almost invariably, results in [imprisonment]."

Whereas in Australia, jurors who break the rules are more likely to get "a stern talking to".

Mr Hunter points to a murder trial in WA that was forced into mistrial by juror misconduct.

"The judge said to the juror words to the effect of, 'No-one, I can assure you, in this entire state is more angry than I am right now' — but that's it."

Emotional and financial cost to breaking rules

Another reason jurors might break the rules is because of a lack of understanding about their role, Mr Hunter says.

"They don't [always] understand that their job is to resolve the controversy on the basis of the evidence that is put before them, not for them to go around and investigate and try and work out for themselves what happened.

"I think they need to understand that it's not their job to find out what happened. Their job is to determine whether someone is proven to be guilty beyond reasonable doubt on the evidence that's put before them."

The repercussions of not understanding that, and breaking the rules, are huge.

Mistrials can cost tens of thousands of dollars. "In crime, the vast majority of defendants are legally aided. So in the end, the cost is borne by the public," Mr Hunter says.

That's not to mention the emotional cost.

"It's terribly upsetting to both witnesses and defendants when they get themselves emotionally prepared for [trial] then suddenly it comes to an abrupt end because someone won't do as they're told."

Mr Hunter says over the last few years, there have been some changes to the way judges instruct juries at the start of trials, including, in Queensland, receiving a pamphlet outlining rules and being stepped through its details by the judge.

"And that's a new development, so I do think it's being taken increasingly seriously."