HOUSTON – A lone holdout juror stood between Merck & Company and what would have been a crucial second Vioxx-trial victory when the U.S. federal judge overseeing the case abruptly ruled the case a mistrial, according to jurors.

That fact will take some of the sting out of Merck’s failure to convince the jury it acted responsibly in developing and marketing the painkiller.

The case, in which relatives of Richard “Dicky” Irvin alleged Merck should be held liable for a fatal heart attack he suffered after taking Vioxx for less than a month, was widely seen as the weakest of the three cases to be tried so far. The jury didn’t appear swayed by the plaintiff’s arguments, initially voting 7 to 2 in favor of Merck. Jurors said they thought Merck made stronger scientific arguments, and that Irvin had a high risk of suffering a heart attack anyway.

“When taken in totality, I don’t think it was Vioxx,” one juror said. “Personally, I felt like if it had been more of a class action or more of a general lawsuit, it would have been a different outcome. Pertaining to Dicky individually, he had too many risk factors to be able to say substantially that Vioxx contributed to his death.”

Despite its near win, the Whitehouse Station, N.J., company faces a tough road. More than 6,500 Vioxx cases have been filed against it, and its failure to win what appeared to be one of the weakest cases didn’t inspire confidence among investors. Yesterday, Merck shares fell 72 cents, or 2.5%, to $28.41 in composite trading on the New York Stock Exchange. About 24.2 million shares changed hands, more than double normal daily volume.

Merck will have to defend itself in this case again. U.S. District Court Judge Eldon E. Fallon said early yesterday that the nine members of the jury had deliberated for a “reasonable” length of time, and dismissed them. The jurors had told the judge that they were deadlocked during an unusual Saturday session he had called to speed the trial along. He asked them to continue trying to reach a decision, but early yesterday apparently concluded they were unlikely to do so.

Judge Fallon said he would meet with lawyers for both sides as early as next week to reschedule the trial, which he said he hoped to hold in New Orleans. Judge Fallon is normally based in New Orleans, but he moved this trial to Houston because of Hurricane Katrina.

Lawyers for both sides said they were disappointed with the outcome. “We are going to keep fighting,” the plaintiff’s attorney in the case, Jere Beasley, said. “It’s a tie, but we believe we came up better than they did.”

The lead defense attorney for Merck, Phil Beck, said he was hoping that Judge Fallon would decide to retry the case in February in place of another federal case that had been scheduled. The roughly 3,000 federal cases have been consolidated under Judge Fallon, who has said he intends to try several representative cases early next year before determining whether a settlement can be reached.

“We’re disappointed, we hoped we’d get a verdict,” Mr. Beck, of the law firm Bartlit Beck, said. “Sometimes that’s how the system works. We’re looking forward to the case in February.”

Mr. Beck, a noted defense attorney hired by Merck to handle the trial, said he didn’t believe the company would change its strategy for the retrial and that he expected to handle the case. “I feel we put on a good case on the science and causation and the plaintiffs did a good job as well.”