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Dependent Claims May Be Definite Although The Independent Claim Is Not


While limitations provided by dependent claims could render those claims definite, even though they depend on indefinite independent claims, inadequate presentation of that issue on appeal operates as a waiver of this argument, a Federal Circuit panel concludes in Halliburton Energy Services, Inc. v. M-I LLC(doing business as M-I Drilling Fluids L.L.C.) (No. 2007-1149; January 25, 2008).

Halliburton owns a patent at issue that relates to oil field drilling fluids. Halliburton sued M-I, alleging that M-I’s drilling mud system infringed certain claims of the patent which recite certain fragile gel drilling fluids. During prosecution, the claims were distinguished from prior art fluids by stating that the claims were “limited to” a “fragile gel” drilling fluid or the method of using a “fragile gel” drilling fluid. After a combined Markman and motion hearing, the district court granted M-I’s motion for summary judgment, finding that all asserted claims of the patent were invalid as indefinite.

A Federal Circuit panel affirms the lower court’s decision, concluding that neither Halliburton’s proposed definition nor any other possible construction resolves the ambiguity in the scope of the term “fragile gel,” and that independent claims containing that term are indefinite. While Halliburton, on appeal, raised the assertion that the district court erred in finding that the asserted dependent claims stood or fell with the independent claims, it did so only in a single sentence, without identifying the dependent claims at issue, and provided no basis for finding them definite if the independent claims are indefinite.


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