When prosecuting a patent application before the Patent Office, applicants often make certain arguments on the record about why prior art references are not applicable to the claimed invention. These statements, however, can (and will be) used against the Applicant in any later litigation involving the claimed invention. The legal structure controlling how these situations can be used to limit claim scope is referred to as "prosecution disclaimer."
In a recent case involving MIT, the Federal Circuit analyzed the requirements for prosecution disclaimer. The case involved whether certain claimed elements relating to "vascularized organ tissue" included skin. During prosecution, extensive prior art was cited relating to skin (but only the think outer layer) and MIT took numerous different approaches with distinct claim language and corresponding declarations to try and distinguish the prior art. MIT tried to claim non-skin structures, but later abandoned this approach. MIT also tried certain thickness limitations, but likewise abandoned that approach. Finally, MIT settled on the "vascularized organ tissue" limitations and was successful in convincing the examiner to allow the application.
In describing the applicable legal rules, the Court summarizes as follows:
"The doctrine of prosecution disclaimer . . . preclud[es] patentees from recapturing through claim interpretation specific meanings disclaimed during prosecution.” Omega Eng’g, Inc. v. Raytek Corp., 334 F.3d 1314, 1323 (Fed. Cir. 2003). “[I]n order for prosecution disclaimer to attach, the disavowal must be both clear and unmistakable.” 3M Innovative Props. Co. v. Tredegar Corp., 725 F.3d 1315, 1325 (Fed. Cir. 2013). This case therefore requires that we analyze whether statements MIT made during the prosecution of the asserted patents amount to a clear and unmistakable disclaimer limiting the meaning of the claim terms. “Where the alleged disavowal is ambiguous, or even ‘amenable to multiple reasonable interpretations,’ we have declined to find prosecution disclaimer.” Avid Tech., Inc. v. Harmonic, Inc., 812 F.3d 1040, 1045 (Fed. Cir. 2016) (quoting Cordis Corp. v. Medtronic AVE, Inc., 339 F.3d 1352, 1359 (Fed. Cir. 2003) and citing Omega Eng’g, 334 F.3d at 1325 (“[W]e have thus consistently rejected prosecution statements too vague or ambiguous to qualify as a disavowal of claim scope.”)). “The party seeking to invoke prosecution history disclaimer bears the burden of proving the existence of a ‘clear and unmistak- able’ disclaimer that would have been evident to one skilled in the art.” Trivascular, Inc. v. Samuels, 812 F.3d 1056, 1063–64 (Fed. Cir. 2016)."
An important aspect of prosecution disclaimer is that the statements must be analyzed in context, including the overall statements and the limitations of the then-pending claims. Here, the court dismissed statements that in isolation would have seemed to disclaim skin as an organ by considering them "in the context of the prosecution history as a whole." The cited statements were insufficient to establish prosecution disclaimer because the statements, including detailed declarations, were directed to claim limitations no longer present in the issued claims. Further, the court looked at the statements from the point of view of a skilled artisan, in terms of whether the skilled artisan would "read the statements in context as limiting the invention to any particular organ or as excluding skin."
This case illustrates that in applications having extensive prosecution history, it can be helpful to the patentee to vary claim language and wording, including significantly adjusting claim limitations late in prosecution. Of course, to be able to make such amendments the specification must be originally prepared to support different claim language. Not only can new language enable a reset with an Examiner that may be entrenched against certain wording, but it can also minimize extensive statements already on record made with respect to no longer present claim limitations.