The plaintiff in this case sought to exclude an expert’s obviousness opinion on several grounds, including failure to identify specific prior art combinations, mere conclusory statements on the motivation to combine, discussion of the inventors’ path and reliance on commercial motivations. While the district court rejected all but one of these grounds, noting that the threshold for precluding expert opinions is less critical in a bench trial setting, the district court agreed that the portion of the expert opinion that addressed the inventors’ path was inadmissible.
Specifically, the expert dedicated several pages in his report to discussing the plaintiff’s internal documents and deposition testimony of the inventors, which, according to the expert, demonstrated that the inventors followed a routine and obvious procedure to select a particular salt with expected properties. The expert then concluded that this path taken by the inventors in formulating the patented compound was obvious, which therefore provided further support for his own independent determination of obviousness.
Despite the expert’s clarification that his discussion of how the inventors arrived at the invention was not necessary for his obviousness determination, the district court nevertheless excluded this portion of the opinion. In doing so, the district court adhered to the Federal Circuit’s cautionary guidance against using the inventor’s path to render an invention obvious, as this would constitute hindsight, and therefore could never lead to a conclusion of obviousness. The district court further pointed to the defendant’s failure to show that the expert’s discussion of internal documents and inventor testimony described “routine testing”—which may be permissible under particular facts—and not an inventive “trial and error procedure” used to discover new compounds. By evaluating the obviousness of the invention through the eyes of the inventor, the district court found that the expert blurred the lines between the inventors’ work and the prior art, as well as between the level of ordinary skill in the art and the inventors’ potentially exceptional skill in the art. For this reason, the district court agreed to exclude those portions of the expert opinion from the bench trial.
Practice Tip: Even in the context of a bench trial, where the exclusion of expert testimony is less critical, experts should not exclusively rely on evidence of the inventive path taken by the inventors when making an obviousness determination. Because viewing the invention with the inventor’s own blueprint fails to properly evaluate the invention in the state of the art that existed at the time, courts are likely to view such evidence as impermissible hindsight. Accordingly, to the extent experts cite evidence of the steps the inventors took to arrive at the invention, they should also include additional, independent bases for obviousness, in the event the “inventors’ path” evidence is excluded.
Exelixis, Inc. v. MSN Laboratories Private Limited et al., 1:19-cv-02017 (D. Del. Apr. 20, 2022).