Appeals court narrows landmark patent ruling – a little

The case concerns robotics company Festo Corporation of Long Island, New York. In 1988, Festo challenged a Japanese rival, Shoketsu Kinzoku Koygo Kabushiki, alleging patent infringement. The federal court ruled that there was no infringement. Significantly, it added that Festo lost certain rights in its technology as soon as it narrowed its original claim for a patent.

Until the Festo case, elements of an invention stripped from a patent claim during amendment were still considered the property of the inventor under US law, even if they did not appear in the formal patent description. Very few US patent applications succeed without some degree of amendment, so the decision, in November 2000, made inventors nervous. It threatened to render thousands of patents worthless.

In May 2002, the US Supreme Court limited the scope of the earlier decision, stating that amending patent claims does not automatically strip patent-holders of equivalence protection.

The ruling went on to say that amending a patent claim creates a presumption that the amendment was intended to narrow the claim, and should therefore not apply. If that presumption is not rebutted, the protection of the equivalents doctrine will fall.

The Supreme Court ruled that the presumption could be rebutted by showing:

• that the amendment involved a feature that was "unforeseeable at the time of the application";
• that the amendment had "no more than a tangential relation" to the equivalent in question; or
• "for some other reason" it could not be included in the original claim.

The case was then sent back to the Federal Court of Appeal, so that the circumstances of the dispute could be reconsidered in light of the new presumption, and its exceptions. It is this ruling that was issued on Friday.

The Court concluded that deciding whether the exceptions applied in any particular case was a question for a judge, not a jury. It then looked at the exceptions and, in an 11-2 majority opinion, offered general guidance on how these were to be interpreted.

The unforeseeability exception, said the court, depended on "the state of the art and the understanding of a hypothetical person of ordinary skill in the art at the time of the amendment". It was a factual exception, said the court, and additional evidence would be necessary to consider it properly.

The tangentiality exception, on the other hand, depended on "on the patentee's objectively apparent reason for the narrowing amendment," which the court could determine for itself, and needed no additional evidence. In Festo's case, said the court, the exception did not apply.

The "other reason" exception was also to be narrowly interpreted. According to the majority opinion:

"it is available in order not to totally foreclose a patentee from relying on reasons, other than unforeseeability and tangentialness, to show that it did not surrender the alleged equivalent. Thus, the third criterion may be satisfied when there was some reason, such as the shortcomings of language, why the patentee was prevented from describing the alleged equivalent when it narrowed the claim."

Again, this exception did not apply to Festo, and so the court remanded only the question of foreseeability to the district court for decision.

The opinion is being seen as a slight shift back towards the strict position adopted by the Federal Court first time around.