NEW YORK (CNN/Money) - Merck's lawyers attacked potentially damaging testimony from a medical examiner in the first Vioxx lawsuit and filed a motion Thursday to prevent her from testifying before jurors in a Texas courtroom.

Former Texas medical examiner Maria Araneta testified on Tuesday before lawyers and Judge Ben Hardin but not before jurors that Robert Ernst, a 59-year-old triathlete and Vioxx patient, died in 2001 from a blood clot or heart attack, according to a lawyer representing Ernst's widow.

The testimony is potentially damaging to Merck & Co. (up $0.07 to $31.29, Research) The plaintiff in the case, Carol Ernst, blames Vioxx for her husband's death and has sued the company.

Merck's defense team filed a motion requesting that Araneta be blocked from testifying before the jury. The motion says that Araneta "was not timely designated as a person with knowledge of relevant facts or an expert witness in this case. Moreover, because plaintiff waited until the day of trial to identify Dr. Araneta, Merck is not able to evaluate properly and respond fully to her opinions."

Before filing the motion, Merck defense lawyer Jonathan Skidmore said at the trial, "[Araneta's] appearance is surprising, considering she was not on the plaintiff's witness list as required by Texas rules."

Ernst's lawyer, W. Mark Lanier of Houston, said that Araneta's testimony in Texas Superior Court proves that Vioxx caused the death of Robert Ernst. Lanier acknowledged he paid $6,000 to fly Araneta from the United Arab Emirates, where she now works, to testify at the trial in Angleton, Texas.

But Merck defense lawyer Skidmore attacked Araneta's testimony as inconsistent with Ernst's autopsy report.

"In the deposition, the coroner testified she can't remember the autopsy," said Skidmore at the trial, according to his firm. "In the autopsy report, which [Araneta] signed, it states there was no evidence of a myocardial infarction and no clot."

Lanier told CNN/Money that Araneta's testimony "matches her autopsy perfectly" and Merck's lawyers were misrepresenting her.

"Big mistake on Merck's part," said Lanier. "They deliberately misled the jury on what Araneta's autopsy meant, figuring I would not put her on the stand."

Merck has consistently asserted that Vioxx is not the proven cause of Ernst's death and the motion refers to Araneta's autopsy as "arguably one of the most critical pieces of evidence in this case."

The lawsuit by Carol Ernst is just the first of more than 4,100 lawsuits filed against Merck because of Vioxx.

Chris Shibutani, an analyst for J.P. Morgan Securities, recently estimated that Merck's liabilities for Vioxx range from $8 billion to $25 billion, the highest estimate so far. Shibutani rates the company "neutral."

Araneta is not the only weapon in Lanier's arsenal. On Thursday jurors heard testimony from David Egilman, a public health professor at Brown University. Egilman resisted Merck sales reps after Vioxx went on the market in 1999 and refused to prescribe the drug at his former family clinic because he did not believe it was safe, according to Lanier.

In separate testimony on Wednesday, Merck scientist Nancy Santanello acknowledged that her company did not change the Vioxx warning label after a study showed that it escalated the risk of heart attacks, according to Lanier and news reports. Santanello testified that Merck persuaded regulators to move language on Vioxx's potential heart attack risks to a less prominent place on the drug's label.

Merck has consistently denied allegations that it concealed the health hazards of Vioxx, noting that it voluntarily withdrew the drug last Sept. 30 because of health concerns.

"Merck acted responsibly, from researching Vioxx prior to approval in clinical trials involving almost 10,000 patients to monitoring the medicine while it was on the market to voluntarily withdrawing the medicine when it did," said Jarrell, the spokesman for Merck's defense lawyers.

Based in Whitehouse Station, N.J., Merck is one of the largest and oldest drugmakers, with $22.9 billion in 2004 sales.

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