A case decided this month by the Federal Circuit Court of Appeals involving technology for preparing multi-cryopreserved liver cells reminds how critical experts can be in deciding patent disputes, including in the context of preliminary proceedings.

The patent involved in Celsis In Vitro, Inc. v. Cellzdirect, Inc. concerns mechanisms for the preservation of liver cells through multiple freezing processes, which enables researchers to have increased access to cell samples over time, and a larger population of donors. Celsis brought suit alleging infringement and, following limited discovery and an evidentiary hearing, obtained a preliminary injunction barring the sale of the accused products.

The principal issues on appeal were the correctness of the trial court’s conclusions as to infringement and validity (that the patented method was not obvious in view of the prior art), as well as the determination of irreparable harm. Applying the abuse of discretion standard of review applicable to rulings on preliminary injunctions, the Federal Circuit relied heavily on the district court’s assessment of expert testimony (or lack thereof) in affirming the injunction.

On the infringement issue, the district court heard testimony from the parties’ competing experts and found the patent owner’s expert was “helpful in carefully explaining how [the defendant’s] accused process [met] all the limitations of the asserted claims” whereas the defense’s experts “didn’t offer anything in the way of opinions to address the proper interpretation of the patent’s claims.” Finding the plaintiff’s expert more persuasive, the district court had ruled that the patent owner was likely to succeed on its claim, weighing in favor of the issuance of an injunction. On appeal, the Federal Circuit held that the district court did not abuse its discretion in finding a likelihood of success as to infringement.

Similarly, the Federal Circuit deferred to the district court’s determination that the testimony of the defense’s experts on issues of obviousness were not credible, opining that the district court “has wide discretion to weigh expert credibility” and the Federal Circuit will defer to those determinations.

On the issue of irreparable harm, the district court found that Celsis would suffer irreparable harm in the form of price erosion, loss of goodwill, damage to reputation and loss of business opportunities based on the unrebutted expert testimony of Celsis’ expert. The Federal Circuit held that there was “no error in the district court’s reliance on Celsis’ unrebutted expert testimony” and based on such testimony, found no reason to revise the district court’s fact determinations. Relatedly, on the district court’s conclusions regarding the balance of harms weighing in Celsis’ favor, the Federal Circuit opined: “This preliminary injunction factor is also affected by [the defense’s] decision not to present expert testimony to rebut Celsis’ expert testimony.”

The Celsis case highlights the significance of both the credibility of dueling experts on issues before the court, as well as the determination of whether to present rebuttal expert testimony.