NEW ORLEANS, May 30 (AP) — A federal judge has ordered a third trial in a lawsuit by a woman who blamed Merck’s painkiller Vioxx for the heart attack that killed her husband.

A cardiologist who testified for Merck misrepresented his qualifications in the second trial last year, Judge Eldon E. Fallon of the Eastern District of Louisiana ruled.

Jurors in that trial ruled in favor of Merck and against Evelyn Irvin Plunkett, whose first husband, Richard Irvin Jr., died of a heart attack after taking Vioxx for less than a month.

The ruling was signed Tuesday, but was made available on the Internet a day later.

The first trial, held in Houston during November and December 2005, ended with the jury deadlocked 8 to 1 in Merck’s favor, two jurors told The Associated Press.

The cardiologist, Dr. Barry Rayburn, a professor of medicine at the University of Alabama, Birmingham, who was hired by Merck as a $600-an-hour expert witness, testified in the second trial that the drug could not have caused Mr. Irvin’s heart attack. Dr. Rayburn testified then that he was board-certified in cardiovascular disease.

When Merck brought Dr. Rayburn as a witness in a second Vioxx trial, in a state court case in New Jersey, however, he testified during cross-examination that his board certification had lapsed.

The ruling will not affect other cases because Dr. Rayburn took the board examinations for recertification last summer, has testified in only those two cases and has since been recertified, his lawyer said.