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Plaintiffs in Lipitor Lawsuit Appeal Dismissal of Expert Testimony to Federal 4th Circuit Appeals Court

A month after a multi-district class action lawsuit against Pfizer’s anti-depressant drug Zoloft was dismissed after a judge excluded the plaintiffs’ expert witnesses, a similar battle is being fought by plaintiffs seeking damages from Pfizer for alleged injuries caused by the company’s cholesterol drug, Lipitor. As was the case in the Zoloft trial, the current litigation focuses on standards of qualifications for experts, and could impact future mass-tort litigation against drug companies.

Lipitor Plaintiffs Petition Court for Expert Witnesses

Plaintiff attorneys representing a multi-district class action litigation made up of more than 3,100 lawsuits over Pfizer’s OTC cholesterol drug Lipitor are petitioning a federal court of appeals to overturn a lower court decision excluding expert witnesses.

According to the Lipitor plaintiff’s lead attorneys, a lower federal court judge erred in striking several expert witnesses who could have connected use of Lipitor with diabetes in female patients. The experts, one of whom was similarly dismissed in the Zoloft decision in June, relied on statistical analysis of available data on Lipitor use and diabetes diagnoses in order to advance the plaintiff’s argument that the cholesterol drug had serious health side effects.

Nicholas Jewell, a professor of biostatistics at the University of California – Berkeley who provided expert testimony in the Zoloft trial which arguably demonstrated a statistically significant link between Lipitor and diabetes, was dismissed due to methodology concerns. Just as with his testimony in the Zoloft trial, the federal judge had issues with Jewell’s methodology, citing concerns that the work was inconsistent in its statistical techniques.

Judge Richard Gergel also dismissed another plaintiff causation expert, Dr. Sonal Singh, who is an internist and associate professor at the University of Massachusetts Medical School. Gergel found Singh’s inability to show a statistically significant connection to diabetes when patients took doses of less than 80 milligrams to be fatal to his testimony, and thus ruled him ineligible.

The plaintiff’s appeal of Gergel’s expert witness orders argues that the two experts are not only qualified to testify, but that they used reliable statistical methodology in order to show a link between Lipitor and diabetes. Amicus briefs submitted by professors who are experts in statistical analysis have been submitted to the appeals court to aid the case for reversing Gergel’s decision and permitting causation testimony from Jewell and Singh.

Pfizer Supports Higher Standards for Expert Witnesses

At the other side of the litigation stands Pfizer, whose attorneys have responded to the appeal with the same arguments which were successful in the Zoloft litigation: that the plaintiff’s experts are not qualified, and judges should rely on heightened standards for expert witness qualification.

According to Pfizer’s legal team, judges under the Daubert standard must serve as strict gatekeepers of expert witnesses in order to keep so-called “junk science” out of the courtroom. According to the defense, plaintiffs in mass-tort drug cases must be required to show that expert witnesses use “an objective, principled basis” for their review of evidence, and absent that, the judge is “justified in concluding that [the experts] are engaged in something other than science.”

Pfizer maintains that the plaintiffs “failed to produce the required reliable expert evidence that Lipitor caused their alleged injuries,” and successfully argued to Judge Gergel that the statistical analysis presented by Jewell and Singh was insufficient in both methodology and conclusion.

On appeal, Pfizer will continue to push for a high standard of review for judges who operate as evidentiary gatekeepers under the Daubert approach — an argument which has worked for them throughout both the Zoloft and Lipitor litigation.   Should the Court of Appeals for the 4th Circuit agree with Pfizer and take the same approach as the 3rd Circuit did in the Zoloft litigation, thousands of Lipitor plaintiffs will have their cases dismissed before trial.

Lipitor Trial another Battle of Expert Witness Standards

As with the Zoloft case, the Lipitor litigation will represent another important and impactful legal skirmish over standards for expert witnesses. The Daubert standard of expert witness review asks judges to be gatekeepers of testimony, and typically provides them a great deal of decision-making latitude in the process. As a result, litigants will often push for a standard of review — either broad or strict — which supports their side, both of which have theoretical merit.

Higher standards for review of experts would allow judges to dismiss testimony if they are uncertain that the methodology is reliable or the expert is qualified, which protects the legal system from unscientific and unreliable methodology.

However, there are concerns that judges — who are commonly not well versed in statistics, science, or any other of a variety of fields that experts represent — can make critical errors by dismissing an expert based on a misunderstanding of the work which went into generating the proposed testimony.

The challenge of finding a balance between keeping bad science out and allowing good science in plays out regularly in courtrooms, with high profile litigation like the Lipitor and Zoloft cases serving as bellwethers for future mass-drug lawsuits.

Expert Opinion Excluded from Evidence in Lipitor Case

Expert Opinion Excluded from Evidence in Lipitor Case

A number of individuals have filed federal lawsuits alleging that their use of the cholesterol-lowering drug Lipitor caused them to develop Type 2 diabetes. The lawsuits have been consolidated in a federal district court in South Carolina.

When large numbers of cases are consolidated in one court under federal rules governing multidistrict litigation, a single case is chosen for trial. That case, known as the “bellwether,” is chosen because it is representative of the other cases awaiting trial. The outcome of the bellwether case may encourage settlement of the remaining cases. It also helps the other litigants assess the risks and costs of taking their cases to trial.

Products liability cases against drug manufacturers necessarily hinge on expert testimony. The judge presiding in the multidistrict Lipitor litigation recently concluded that one of the expert witnesses designated by the plaintiffs in the bellwether case would not be allowed to testify that Lipitor causes Type 2 diabetes.

The Hempstead Case

Juanita Hempstead’s case was chosen as the bellwether. Hempstead was given a prescription for Lipitor in March 1998. She started taking it in June 1999 but did not take it consistently until July 2000. Her lipid levels (including her level of total cholesterol) were higher than normal before she began regular use of Lipitor. Her blood glucose level was normal when it was tested in 1999.

In 2002, Hempstead’s lipid levels were normal. Her glucose level, however, was abnormal. It was in a range that is classified as pre-diabetic. In 2003, Hempstead stopped taking Lipitor for three weeks because she was experiencing abdominal pain. At the end of the three weeks, her lipid and glucose levels were higher than they were in 2002. She resumed use of Lipitor and, three months later, her lipid levels returned to normal.

In February 2004, Hempstead was hospitalized for colitis. Her glucose reading at that time was in the diabetic range. Three months later, her glucose level was substantially higher and she was diagnosed with new-onset diabetes. Hempstead’s weight apparently increased steadily between 1998 and 2004.


Hempstead was required to prove both general and specific causation. To prove general causation, she needed evidence to establish that Lipitor is capable of causing diabetes. To prove specific causation, she needed evidence that Lipitor actually caused her diabetes.

The district court took note of cases that require no proof of specific causation if studies of general causation establish that taking a drug at least doubles the risk of sustaining the injury for which the plaintiff is suing. Those cases hold that if most people who take a drug experience the harm that the plaintiff experienced, no additional proof of causation is necessary, at least if the plaintiff’s characteristics and use of the drug were similar to those of the subjects who participated in the study that established the risk.

Studies cited by Hempstead’s experts established that taking Lipitor increases the risk of developing diabetes by a factor of 1.6. Since that is less than a doubling of risk, Hempstead was required to prove that Lipitor actually caused her diabetes. She relied on Dr. Elizabeth Murphy to prove specific causation.

Daubert Analysis

The court based its decision on Rule 702 of the Federal Rules of Evidence, as interpreted by the Daubert decision. That rule requires the trial judge to assure that an expert’s testimony will be both relevant and reliable. The reliability of scientific opinions is measured by whether the expert reasonably applied reliable principles and methods to sufficient facts or data.

The court noted that in its role as gatekeeper, it must not substitute its own view of expert opinions for the view that a jury could reasonably take. At the same time, the court has an obligation to protect the integrity of the jury’s decision by assuring that expert evidence, which has the potential “to be both powerful and quite misleading,” is based on a reliable methodology.

Dr. Murphy is a Professor of Clinical Medicine and the Chief of the Division of Endocrinology at San Francisco General Hospital. She has an M.D. from Harvard and a Ph.D. in biochemistry from Oxford. Her credentials to testify as an expert were clear, so the question was whether her opinion that Hempstead’s diabetes was caused by Lipitor was rooted in a reliable methodology.

The court characterized Dr. Murphy’s opinion as being based on (1) the fact that Lipitor increases the risk of diabetes (general causation) and (2) the fact Hempstead developed diabetes after taking Lipitor. Dr. Murphy’s deposition testimony disclosed no fact other than the temporal relationship between using Lipitor and the onset of diabetes that supported her opinion of a causal relationship between the two.

The court faulted Dr. Murphy for failing to rule out other risk factors that might have caused the onset of Hempstead’s diabetes, including her weight gain and a corresponding increase in her body mass index (BMI). Hempstead’s family history, age, and struggle with hypertension were also factors that could have caused her diabetes. The court concluded that Dr. Murphy’s opinion was unreliable because she did not determine whether Hempstead would have developed diabetes without taking Lipitor and did not compare the magnitude of the risk of diabetes onset associated with taking Lipitor to the magnitude of the risk that existed if Hempstead had not taken Lipitor.

Court Excludes Expert Opinion

It may be that the public interest would best be served by holding drug companies accountable for increasing a patient’s risk of contracting a disease, even when it cannot be established that the patient fell within the significant percentage of drug recipients whose disease was caused by the drug rather than the percentage who would have contracted the disease anyway. That, however, is not the law that governed the District Court’s decision.

Because Dr. Murphy’s testimony did not move beyond general causation to establish a specific link between Hempstead’s use of Lipitor and her development of diabetes, the district court barred Dr. Murphy’s testimony on the ground that her opinion about specific causation had no scientific basis. Whether Hempstead’s case will be able to move forward, and how the ruling will affect other Lipitor cases, are issues that will likely be decided in the coming weeks.