In an effort to further improve quality of United States patents, the USPTO implemented patent re-examination procedures; ex parte -1980; and inter partes – 1999. Anyone, including those who wish to remain anonymous, may request re-examination of any US patent in force. The request must be based upon prior art not previously considered. The patent office will grant a re-examination request if they find a “substantial new question of patentability” in view of the newly submitted art. Alternatively, the patent office my reject the re-examination request and the patent will not be subject to re-examination.

If a re-examination is ordered, the patent office will likely form new claims rejections to at least some of the patent claims. The patentee will have the opportunity to argue in favor of patentability in a fashion identical to a conventional patent examination. In an ‘ex parte re-examination’, the requestor is not permitted participation in the process and the patent examiner is solely responsible for arguing the case against patentability. In an ‘inter partes re-examination’, the requestor is permitted limited participation and comment which may influence the re-examination process.

At the conclusion of a patent re-examination, the patent office will issue a re-examination certificate where all claims may be adjusted, some claims may be adjusted, or no claims are adjusted. The patent may be entirely invalidated, or not changed at all, or somewhere in between.

The result of a patent re-examination is appealable by the patentee. First, appeal may be taken to the Board of Patent Appeals and Interferences. Upon unfavorable results there, an appeal may be further brought to the Court of Appeals, Federal Circuit. All the while, the patent may remain enforceable and patent litigation may come despite commencement of any re-examination. However, in some cases a patent infringement court may stay a proceeding until the final outcome of a patent re-examination is realized.