Federal Circuit affirms practice of reviewing trial judges’ patent claim interpretation rulings anew

In a newly issued opinion, the Federal Circuit has affirmed its long-standing practice of reviewing trial court claim construction rulings de novo, as a question of law, while issues of fact will continue to receive deference by the reviewing appeals court.

Under US law generally, questions of law are reviewed anew (de novo, or without deference to the trial court) by an appellate court. On questions of fact, however, trial courts do receive deference by the reviewing appeals court.

The question arises, then, what to do with an issue that is both. As the Supreme Court has found, determining the meaning of a patent claim term is a ‘mongrel practice’ of law and fact with ‘evidentiary underpinnings’. In a much anticipated decision handed down on 21 February 2014, the Federal Circuit held, six to four, that it will continue to review claim construction rulings by trial courts anew, as a question of law…

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