Last week, a juror in a big federal drug trial in Florida admitted to the judge that he had been researching the case on the Internet, directly violating the judge's instructions and centuries of legal rules. But when the judge questioned the rest of the jury, he got an even bigger shock.
Eight other jurors had been doing the same thing. The federal judge, William J. Zloch, had no choice but to declare a mistrial, wasting eight weeks of work by federal prosecutors and defense lawyers.
"We were stunned," said the defense lawyer, Peter Raben, who was told by the jury that he was on the verge of winning the case. "It's the first time modern technology struck us in that fashion, and it hit us right over the head."
It might be called a Google mistrial. Jurors' use of BlackBerrys and iPhones to gather and send out information about cases is wreaking havoc on trials around the United States, upending deliberations and infuriating judges.
Last week, a building products company asked an Arkansas court to overturn a $12.6 million judgment against it after a juror in the civil trial used Twitter to send updates during the proceedings.
On Monday, defense lawyers in the federal corruption trial of a former Pennsylvania state senator, Vincent J. Fumo, demanded that the judge declare a mistrial after a juror posted updates on the case on Twitter and Facebook. The juror even told his readers that a "big announcement" was coming on Monday. But the judge decided to let the trial continue, and the jury found Mr. Fumo guilty. His lawyers plan to use the Internet postings as grounds for appeal.
Jurors are not supposed to seek information outside of the courtroom. They are required to make their decision based only on facts that the judge has decided are admissible, and they do not see evidence that has been excluded as prejudicial. But now, using their own cellphones - to look up the name of a defendant on the Web or to examine an intersection using Google Maps - they violate the legal system's complex rules of evidence. They can also tell their friends what is happening in the jury room, though they are supposed to keep their opinions and deliberations secret.
Such cases are not confined to the United States. In Britain, a juror went online not long ago with a Blackberry during a trial for rape, causing the conviction to be quashed. The Lord Chief Justice, Lord Judge of Draycote, made a recent speech where he noted that some jurors have been found making "private enquiries" on the Internet despite orders not to.
A juror on a lunch or bathroom break can find out many details about a case. Wikipedia can help explain the technology underlying a patent claim or medical condition, Google Maps can show how long it might take to drive from point A to point B, and news sites can show what has been written about a criminal defendant, his lawyers or expert witnesses.
"It's really impossible to control it," said Douglas L. Keene, president of the American Society of Trial Consultants.
Judges have long amended their habitual warning about seeking outside information during trials to include Internet searches. But with the Internet now as close as jurors' pockets, the risk has grown more immediate - and instinctual. Now lawyers have routinely begun to check the blogs and Web sites of prospective jurors.
Mr. Keene said jurors might think they are helping, not hurting, by digging deeper. "There are people who feel they can't serve justice if they don't find the answers to certain questions," he said.
But the rules of evidence, developed over hundreds of years of jurisprudence, are there to ensure that the facts that go before a jury have been subjected to scrutiny and challenge from both sides, said Olin Guy Wellborn, a professor at the University of Texas law school.
"That's the beauty of the adversary system," said Mr. Wellborn, a co-author of a handbook on evidence law. "You lose all that when the jurors go out on their own."
In the Florida case that resulted in a mistrial, Mr. Raben, a defense attorney from Miami, spent nearly eight weeks fighting charges that his client illegally sold prescription drugs through Internet pharmacies. The arguments were completed and the jury was deliberating over the verdict when one of them contacted the judge to say another juror had admitted to her that he had done some outside research on the case over the Internet.
As the judge questioned the juror about his research - which included evidence that the judge had specifically excluded - Mr. Raben recalled thinking that if the juror had not communicated his information to the rest of the jury, "we can just kick this juror off and go" on with the trial, instead of wasting eight weeks.
But the judge then found that eight other jurors had done the same thing, Googling the lawyers and the defendant, looking up news stories about the case, checking word definitions on Wikipedia and searching for evidence that had been specifically excluded by the judge. "It was a heartbreak," Mr. Raben said.
In the Arkansas case, Stoam Holdings, the company trying to overturn the $12.6 million judgment against it, said a juror, Johnathan Powell, had sent his Twitter messages during the trial. Mr. Powell's messages included, "oh and nobody buy Stoam. Its bad mojo and they'll probably cease to Exist, now that their wallet is 12m lighter," and "So Johnathan, what did you do today? Oh nothing really, I just gave away TWELVE MILLION DOLLARS of somebody else's money."
Mr. Powell, who is 29 and manages a one-hour photo booth at a Wal- Mart in Fayetteville, Arkansas, insisted in an interview he had not sent any substantive messages about the case until the verdict had been delivered and he was released from any obligation to keep mum. "I was done when I mentioned the trial at all," he said. "They're welcome to pull my phone records."
But juror research is a more troublesome issue than Tweeting or blogging, said Mr. Keene of the American Society of Trial Consultants, and raises new issues for judges in giving instructions.
"It's important that they don't know what's excluded, and it's important that they don't know why it's excluded," Mr. Keene said. The court cannot even give a full explanation to jurors about research - say, to tell them what not to look for - and so instructions are usually delivered as blanket admonitions, he said.
The technological landscape has changed so much that today's judge, Mr. Keene said, "has to explain why this is crucial, and not just go through boilerplate instructions." And, he said, enforcement goes beyond what the judge can do, noting that "it's up to juror 11 to make sure juror 12 stays in line."
It does not always work out that way. Seth A. McDowell, a data support specialist who lives in Albuquerque, New Mexico, and works for a financial advising firm, said he was serving on a jury last year when a member of the jury admitted having Googled the defendant. He said the juror acknowledged that she was not supposed to do so and said she did not find anything on the Internet.
Mr. McDowell, who is 35, said he wondered whether he should tell the judge, but decided against it. None of the other members of the jury did, either. Now, he said, after a bit of soul searching, he feels he might have made the wrong choice.