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EMPHASIZING “REASONABLE” IN THE “BROADEST REASONABLE INTERPRETATION” STANDARD FOR CLAIM CONSTRUCTION

Daicel Corporation v. Celanese Int’l Corp., No. IPR2015-00171, Paper No. 86 (P.T.A.B. June 23, 2016) sheds important insight on how the Board applies the broadest reasonable interpretation (BRI) standard for claim construction, and the application of intrinsic and extrinsic evidence.  In that case, the Board instituted an IPR based on both § 102(b) and § 103 grounds.  After considering the intrinsic and extrinsic evidence, the Board concluded that the proper construction under BRI was narrower than the literal claim language, and it upheld the patentability of the challenged claims.

The patent at issue (“the ’507 patent”) relates “to the production of acetic acid using a low water process with an iodide salt as a catalyst stabilizer.”  The ’507 patent discloses and claims a process whereby dimethyl ether (DME) is used to inhibit the production of carbonyl compounds, recognized in the prior art to complicate the synthesis of acetic acid.  The disputed claim language included the phrase “overhead stream comprising dimethyl ether.”  Prior art cited by Petitioner discloses a similar production process for acetic acid that Petitioner established would inherently produce some level of DME via side reactions.  Thus, whether the claims of the ’507 patent are anticipated by or would have been obvious in light of the prior art depended on whether the claim language of the ’507 patent includes any amount of DME.

The Board recognized that under the broadest reading of the plain language of the claim, a stream containing any amount of DME would fall within the claim scope.  Daicel Corp., No. IPR2015-00171 at 39.  However, the Board also recognized that the claim must be construed as interpreted by one of skill in the art.  Id. at 28.  Emphasizing the “reasonable” portion of the BRI standard, the Board agreed with the Patent Owner that the intrinsic and extrinsic evidence supported a claim construction requiring an effective amount of DME to inhibit carbonyl production.  Id. at 42.  First, the Board concluded that the specification and prosecution history both suggested the inventor recognized that the addition of DME (beyond the insubstantial amount produced in prior art reactions) remedied the carbonyl problem recognized in the prior art.  Second, the Board relied on expert testimony to establish the state of the art.  Id. at 36-39, 42.  Patent Owner’s expert testified that one of ordinary skill in the art would only consider a species to be present if it had an “effect” on the stream.  Expressly relying on that extrinsic evidence, the Board concluded that one of ordinary skill in the art would have understood the presence of DME in the system described to be referring only to “effective” amounts.  Id. at 42 (“Based on our analysis of the intrinsic and extrinsic evidence, we agree with Patent Owner that a person of ordinary skill in the art would understand the ’507 patent to speak in terms of effects, not molecules.”).

This decision highlights the importance of the “reasonableness” aspect of the BRI standard. While the decision does not deemphasize the importance and weight given to the intrinsic evidence—and indeed relies expressly upon it—it also illustrates the importance that expert testimony can have in claim construction.  Patent owners would be well-advised in the future to establish the ordinary and customary understanding of industry standards and practices through expert testimony in support of their claim construction positions.