In a complicated pharmaceutical mass tort, who better to help the jury understand how drugs are approved in the United States than a former Food and Drug Administration commissioner, right?

Wrong, according to Bayer Healthcare Pharmaceuticals Inc. and Bayer Pharma AG, the creator and marketer of the controversial birth control pill Yaz.

Yaz is the subject of a multi-district litigation in a Benton, Illinois federal court, in which thousands of women alleged that the pill caused a host of side effects, including increased risk of blood clots. The plaintiffs' steering committee wants to present testimony from former FDA commissioner Dr. David Kessler, who submitted an expert report stating that an FDA advisory committee's vote to keep Yaz on the market in December 2011 was tainted by undisclosed potential conflicts of interest.

But for the second time in this MDL, Bayer's lawyers, including teams from Sidley Austin and Bartlit Beck Herman Palencahar & Scott, are challenging Kessler's expert-witness credentials.

As an initial matter, it's worth noting the parties will have time to fight this one out; earlier this month, U.S. District Judge David Herndon (again) postponed the Yaz MDL's bellwether trial. It was scheduled to begin this month but was pushed back to April 20, 2012.

The plaintiffs want to show that the advisory committee had ties to Bayer and Yaz that could be considered impartial. "It is my opinion that the FDA advisory committee was not independent of Bayer," Kessler wrote in his report.

Bayer, however, argued in a Dec. 30 motion that Kessler's new report recites facts but does not demonstrate that he has "knowledge of the relevant facts." Further, Bayer said the former commissioner is offering legal opinions he is not qualified to offer and, perhaps most importantly, he "makes no effort to apply the standards and procedures that the FDA employs to address these conflicts of interest issues" and instead applies his own "unidentified standards."

Herndon has already told Bayer, in no uncertain terms, that he regards Kessler as an expert. In a December 2011 ruling denying Bayer's first attempt to exclude testimony from the former FDA commissioner, the judge chastised Bayer for raising a Daubert challenge instead of bringing an in limine motion (or even simply objecting to plaintiffs' questions at trial). "Kessler's testimony will assist the trier of fact in understanding federal regulations," Herndon wrote. "Kessler may testify as to what a reasonable FDA official would have done with information" about Yaz-related drug clots, he said.

Nevertheless, Bayer may have traction with its new attempt to exclude Kessler's testimony. Drug and Device Law blogger James Beck of Dechert said that the rules relating to impartiality of FDA advisory committee members have changed since Kessler left the FDA in 1997, and that it would be difficult for him to have particular knowledge of the revised rules. In other words, though Herndon came down staunchly on the plaintiffs' side before, he could still have a problem with Kessler opining on what a reasonable official would do if he doesn't know the standard that official should be applying.

But one of the plaintiffs' attorneys, Roger Denton of Schlichter Bogard & Denton, said he expects to prevail on the ruling and that "Dr. Kessler will be able to provide all of his opinions to the jury, as he should be able to do."

It's clear at this point that Kessler, whose recently unsealed report is highly critical of Bayer's behavior in the lead up to the drug's approval, will testify. But the back and forth as to what exactly he can say continues.

Denton serves as plaintiffs' liaison counsel, while Michael Burg of Burg Simpson Eldredge Hersh & Jardine, Michael London of Douglas & London, and Mark Niemeyer of Onder, Shelton, O'Leary and Peterson serve as co-lead counsel. Bayer counsel Susan Weber of Sidley Austin and John Galvin of Fox Galvin did not return a call for comment.

(Reporting by Erin Geiger Smith)

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