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US Supreme Court Clarifies Law of Ambiguity

The US Supreme Court has restated the test for determining whether a patent claim is indefinite (or ambiguous) in its recent decision in Nautilus v. Biosig Instruments.

Justice Ginsburg writing  for the unanimous Court, held  “a patent is invalid for indefiniteness if its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.

The “reasonable certainty” standard represents a different approach to the issue of ambiguity than that previously applied by the Federal Circuit, in which a patent claim was not considered to be indefinite if it was “amenable to construction” and not “insolubly ambiguous.” It is not evident whether the new standard is necessarily a more stringent one, but the test was certainly intended to impart clarity to the analysis. The Supreme Court recognized that the new standard “must take into account the inherent limitations of language” and “mandates clarity, while recognizing that absolute precision is not attainable.”

Following its review of the indefiniteness standard, the Supreme Court did not turn to the patent at issue, but instead remanded the matter to the Federal Circuit for redetermination on the basis of the “reasonable certainty” standard.

The issue arose in the context of an action for the infringement of Biosig’s patent for a heart rate monitor for use during exercise. Nautilus brought a motion for summary judgment on the basis that the patent claims were indefinite. The District Court granted the motion on the basis that the claims did not tell “what precisely the space should be” between each electrode pair in the device. The Federal Circuit reversed, with the majority explaining that the distance cannot be neither “greater than the width of the user’s hands” nor “infinitesimally small.” The Federal Circuit’s application of the revised test will be instructive, and it is notable that although the panel was split on the analysis, it was unanimous in concluding that the patent was not ambiguous.

The approach to claim construction in Canada is broadly similar to that in the United States, with the notable exception that the Canadian prosecution history is inadmissible for the purpose of construction. Canadian claims are also evaluated from the perspective of a person skilled in the relevant art in the light of the patent’s specification. However, in the past decade, the Federal Court of Canada has been reluctant to invalidate patents on the basis of ambiguous claims. In Letourneau v. Clearbrook Iron Works Ltd, 2005 FC 1229, Justice Mosley summarized the Federal Court of Canada’s approach as follows:

The Court must give a purposive construction to a claim without being too astute or technical. If there is more than one construction that can be reasonably reached, the Court must favour the construction which upholds the patent. Where the language of the specification, upon a reasonable view of it, can be read so as to afford the inventor protection for that which he has actually in good faith invented, the court, as a rule, will endeavour to give effect to that construction.

Later in 2005, Justice Hughes (also of the Federal Court of Canada) referred to ambiguity in Pfizer v. Mayne Pharma as a “last resort, rarely, if ever, to be used”, and the Federal Court has consistently used this language when rejecting allegations of ambiguity (most recently in a decision of Justice Gleason in Alcon v. Cobalt). However, unlike in the United States, the test for ambiguity has not recently attracted the attention of Canadian appellate Courts.

A copy of the the U.S. Supreme Court’s Opinion in Nautilus may be found here.