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Prosecution history estoppel prevents a patent owner from contradicting earlier positions taken during the course of his/her patent prosecution. For example, an applicant cannot claim an equivalent subject matter (under the doctrine of equivalents) that he/she previously disavowed. during the prosecution. Thus, any amendment made for a patentability-related reason that limits the patent’s scope cannot be broadened in an infringement lawsuit as the applicant will be barred (estopped) from proving that the limitation does not exist.

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