Specification over Dictionary, in US Patent Claims Construction

A recent US Court of Appeals for the Federal Circuit decision has reaffirmed the pre-eminence of the specification over dictionary definitions when construing the meaning of terms of patent claims. The court also clarified when dictionary definitions can be used for patent claim construction. US patent claims are to be interpreted in light of the knowledge of a person of ordinary skill in the art at the time of filing. Such a person is deemed to have read the claims in light of the intrinsic evidence of the inventors lexicography – the patent specification, and file history. Extrinsic evidence concerning relevant scientific principles, the meaning of technical terms, and the state of the art may also be used, but where the definition defined in the specification differs from the generally accepted meaning, the scope as delimited by the inventor governs. The court enunciated a number of deficiencies in extrinsic evidence to further limit reliance on such evidence by future courts, including that the court may undermine the public notice function of patents by relying on extrinsic evidence "in derogation of "˜the indisputable public records consisting of the claims, the specification and the prosecution history' ". Ironically, perhaps, it was the word "baffles" which needed construction in this case. The issue was whether or not the word "baffles" in claim 1, imposed more than the generic limitation of being "load-bearing objects that check, impede, or obstruct the flow of something", i.e. by imposing a limitation on the angle at which they were oriented. The other claims themselves clarified the issue. If the angle of orientation was an implied limitation, then independent claim 1 would have been redundant to claims 2, 6 or 17. To avoid the redundancy, the baffles should be given the broadest meaning supported by the specification. The court affirmed the principle that while limitations need to support each and every claim must be expressed in the specification, all limitations do not need to be imposed in the construction of particular claims where the limitation is unnecessary. In cases such as this, the dictionary definition is general education for the court, which serves to prevent unnecessary limitations from being imposed on the claims. This decision resolves an area of confusion in US patent law, and the result is a rule more in line with Canadian practice. However, practitioners should note that litigants may not use the file history as a tool for claims construction in Canada. For the US Court of Appeals for the Federal Circuit decision in Philips v AWH, 03-1269 (12 July 2005), see: http://fedcir.gov/opinions/03-1269.pdf Summary by: Nicholas J. Whalen