Tostee juror becomes cautionary tale

Queensland judges have begun to use the case of a juror in the Gable Tostee trial who posted on Instagram as a warning to others against repeating the mistake.

The juror almost caused a mistrial in the high-profile murder case last week when it was revealed she had been telling her 2000-plus followers she was deliberating on a high-profile trial and discussing her feelings.

At an unrelated murder trial that began in Toowoomba on Monday, Supreme Court Justice Glenn Martin specifically cited the incident when warning a jury against communicating with the outside world.

The panel was forbidden from discussing the case "in the broadest context possible", he said.

"No texts, Facebook posts, no tweets, no Instagrams, no WhatsApp," Justice Martin said.

"There may be more since I did this list, and I only did it last week."

The Tostee juror's posts were "relatively innocuous", the judge added.

"But it runs the risk, and it's a very real risk, that if a juror does that ... of the entire trial falling over," he said.

The unfairness of that outcome was not just the cost, Justice Martin said.

"The unfairness of that is that the both defendant and all the witnesses come back again.

"There's no need to do that - there's no need for anybody to be communicating in any form about this."

Juries are routinely warned against researching cases online, though not usually in such specific terms.

No action was taken against the Tostee juror but Justice John Byrne, who presided over the case, described her actions as "particularly disappointing".