Last week, a juror in a big federal drug trial in Florida admitted to the judge that he had been doing research on 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.”