Federal Circuit backs Boston Scientific in stent clash

The US Court of Appeals for the Federal Circuit has backed Boston Scientific in its dispute with inventor David Jang, issuing a precedential ruling.

This is the fourth time the court has ruled on the quarrel between the parties.

US patent number 5,922,021, called “Intravascular stent” and owned by Jang, and Boston Scientific’s ‘Express’ stent were at the centre of the clash.

In 2002, Jang assigned the ‘021 patent to Boston Scientific for approximately $50 million.

Under the agreement, Jang was entitled to certain royalty payments (up to $110 million) if Boston Scientific ever developed and sold a coronary stent that was covered by the patent.

In 2005, Jang sued Boston Scientific at the US District Court for the Central District of California, arguing that Boston Scientific’s ‘Express’ stent was infringing and consequently that Jang was owed royalties.

Eight years later, Boston Scientific requested an ex parte re-examination of the asserted claims before the US Patent and Trademark Office (USPTO). The claims were cancelled in the re-examination.

Jang attempted to present a doctrine of equivalents theory to the jury.

The legal rule allows a court to hold a party liable for patent infringement even though the infringing device or process is not identical to the patent claim.

Boston Scientific moved to stop Jang from presenting the doctrine to the jury and invoked an ensnarement defence, insisting that Jang’s doctrine of equivalents would ensnare the prior art. It referenced three patents as prior art.

The jury found no literal infringement, but found infringement under the doctrine of equivalents.

Following the jury verdict, the district court conducted an evidentiary hearing on ensnarement and vacated the jury verdict of infringement.

On appeal, Jang challenged the district court’s removal of the jury’s finding that the stent infringed the asserted claims under the doctrine of equivalents.

The court also issued a judgment of non-infringement in favour of Boston Scientific.

According to Jang, the district court incorrectly held that he had failed to provide an “acceptable hypothetical claim for an ensnarement analysis, and thereby failed to prove that his doctrine of equivalents theory did not ensnare the prior art”.

Boston Scientific cross-appealed, arguing that the district court erred in finding that the company was contractually obligated to pay royalties for past sales of the stent if it infringed the asserted claims, despite the USPTO’s cancellation of the claims in the ex parte re-examination.

The Federal Circuit affirmed District Judge Virginia Phillips’s denial of Jang’s motion for judgment as a matter of law, the court’s removal of the jury verdict, and its judgment of non-infringement.

Because of the affirmation of the judge’s decision, the Federal Circuit dismissed Boston Scientific’s cross-appeal and did not look into the arguments raised.

Circuit Judge Raymond Chen, on behalf of the court, said: “In sum, the district court permissibly conducted a post-trial ensnarement hearing after finding that Boston Scientific timely raised the defence.”

Chen added that the district court appropriately vacated the jury verdict and entered judgment of non-infringement after Jang failed to demonstrate “through a proper hypothetical claim analysis that his doctrine of equivalents theory did not ensnare the prior art”.

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