ATLANTIC CITY, N.J. – Merck prevailed in a crucial Vioxx trial yesterday when a nine-person jury found the company not liable for the heart attack of an Idaho postal worker.

On the third day of deliberations, jurors found the company not liable for two claims brought against it by plaintiff Frederick “Mike” Humeston.

The first claim was that Merck failed to warn the public of Vioxx’s dangers – a claim that included whether Vioxx caused Mr. Humeston’s heart attack in 2001. The second was that the company violated New Jersey’s consumer fraud protection law by intentionally concealing Vioxx’s risks in its sales and advertising practices.

The verdict in the nation’s second Vioxx trial is a major victory for Merck, which lost the first trial in Texas in August. In the Texas trial, jurors awarded $253.4 million to the widow of a man who died after taking Vioxx. That verdict is expected to be reduced under Texas law.

Merck shares rallied on yesterday’s ruling, at one point lifting the company’s market capitalization by more than $4 billion. Recently, Merck shares closed up $1.07 cents at $29.48.The day Merck lost the Texas trial, the company’s shares fell to $28.06, losing $5.2 billion in market capitalization.

Although Merck’s potential Vioxx liability could still be in the billions of dollars, the verdict yesterday signals that the thousands of plaintiffs who have sued Merck over Vioxx can’t necessarily count on big awards, especially those who took the drug for short periods. It also could reinforce Merck’s stated strategy of defending itself against each case, rather than seeking a global settlement.

“Certainly it’s a very positive development for Merck,” the head of Webster Consulting Group, which includes pharmaceutical companies among its clients, David Webster, said.

Mr. Webster said the potential reduction in Merck’s future Vioxx liability also could free cash needed to launch such promising products as a vaccine for cervical cancer.

“This confirms our strategy to continue vigorously defending these suits,” a Merck lawyer, James Fitzpatrick, said outside the courthouse. As for future cases, Merck General Counsel Kenneth Frazier said during a press conference that there were no scenarios in which the company would consider a settlement.

Mr. Humeston’s lawyer, Christopher Seeger, said the outside the courthouse that he was “devastated” for the Humestons. One juror, Vicki Heintz, a 40-year-old resident of Mays Landing, N.J., said she felt Mr. Humeston was sincere in his belief that Vioxx caused his heart attack. However, she agreed with Merck that Mr. Humeston was in poor health before and that it was job-related stress that ultimately caused his heart attack. She also believed that Merck did what it could to ensure Vioxx was safe.

The most important aspect of the victory relates to the jury’s finding that Merck didn’t commit fraud under New Jersey law and fairly represented the drug’s risks.

This ruling has “wide-ranging implications” to other cases, because it will be a recurring theme, a professor at Temple University School of Law, Franklin McClellan, said.

Merck, of Whitehouse Station, N.J., voluntarily withdrew Vioxx from the market in September 2004 after finding that patients who took the drug for 18 months had an increased risk of cardiovascular events such as heart attack and stroke.