A UK juror who allegedly sent messages to a defendant on Facebook will be prosecuted for contempt of court this week after the two women caused a multimillion-pound drug trial to collapse.

In the first case of its kind in the UK the Attorney-General will open contempt proceedings against Joanne Fraill and an acquitted defendant, Jamie Sewart. The move comes as a leading lawyer warned that Britain is heading for "trial by X Factor" - in an apparent reference to the popular TV talent show - unless jurors obey the law on not discussing cases outside court.

The case, to be heard by Lord Judge, the Lord Chief Justice, coincides with an appeal by another defendant in the trial who is challenging his conviction because of the alleged Facebook conversation. The trial had run for nearly three months at a cost of £6 million ($9.7 million).

An investigation by The (London) Times and reported Mtodayshows that jurors in dozens of criminal trials go on to the internet to discuss or research cases. There is evidence of jurors saying that they intend to find a defendant guilty, giving details of deliberations, and running online polls to help to make a decision.

The newspaper found more than 40 examples of postings likely to be in breach of the rules - but the problem is thought to be much greater.

Christopher Kinch, QC, chairman of the Criminal Bar Association, said that comments assuming the guilt of the defendant were possible grounds for appeal. "The situation is a potential time bomb for the jury system. Left unchecked, we could move towards trial by X Factor-type online polling; or jurors might find themselves put under pressure by correspondents online," he said.

The aborted trial involving Fraill, 40, and Sewart, 34, took place in Manchester last year and involved multiple charges and defendants.

One of the defendants, the convicted drug dealer Gary Knox, is appealing against his conviction on the basis of alleged jury misconduct. His appeal will also be heard by Lord Judge.

At the time, the Attorney-General, Dominic Grieve said that the jury had almost reached verdicts but had to be discharged because of Fraill's actions. "That conduct and discussion were in direct breach of the judge's repeated directions to the jury that they should not discuss the case with anyone outside their number, and constituted a contempt of court," he said.

Sewart also faces contempt proceedings because she is alleged to have asked Fraill for details of the jury's deliberations in relation to a charge they were still considering.

Lord Judge is expected this week to send a tough message on internet use by jurors, emphasising that they could risk prosecution. New measures will include warnings from judges to jurors at the start of trials; warnings in the information video shown to jurors before trials and notices in the jury room.

John Cooper, QC, a criminal barrister and member of the Bar Council, said that internet use by jurors was a modern manifestation of an old problem -- how to stop jurors talking about trials.

"We should not overact about this," he said. "The real issue is how to police the use of jurors on social networking sites."

Originally published as Juror prosecuted over Facebook message