Ex parte and inter partes re-examination

The original re-examination procedure, established in 1981, is conducted ex parte. This circumscription of third-party participation, coupled with constraints on the grounds on which re-examination can be requested, has substantially limited the use of ex parte re-examination: in 2003, only 239 third-party requests for ex parte re-examination were filed. Of these, an appreciable fraction were filed in the context of concurrent infringement litigation.

In an attempt to broaden the participatory role of the third-party challenger, Congress established an inter partes re-examination procedure 5 years ago in which the requester participates more fully. Even after statutory amendment in 2002, however, this procedure remains moribund, fatally afflicted by a statutory provision that prohibits the third-party requester from “asserting at a later time, in any civil action ... any ground which the third-party requester raised or could have raised during the inter partes re-examination proceedings”. In 2003, only 21 requests for inter partes re-examination were filed, of which 4 were known to the US Patent and Trademark Office (US PTO) to have related litigation.

Legislation that would establish an adversarial post-grant opposition procedure modelled after that available in the EPO was introduced in Congress in October 2004 (see box), but it seems unlikely to have an early passage.

Request for ex parte re-examination

At any time during the period of a patent's enforceability — from the day of issuance to the sixth anniversary of its expiry — any party can file a request for ex parte re-examination of any one or more of the patent's claims.

The request for ex parte re-examination must allege that prior art raises a substantial new question of patentability of at least one claim. Only printed prior art is cognizable, and the request must allege that the art compromises either the novelty of the claim or its 'originality', establishes the existence of a statutory bar, or calls into question the non-obviousness of the invention. The request can also allege statutory or non-statutory double-patenting over one or more of the patentee's other patents.

The patent office will not consider other grounds for challenging validity, such as improper inventorship, inequitable conduct, public use, failure of the patentee to disclose the best mode or the existence of an invalidating prior sale, and will only consider the adequacy of the specification's written description and enabling support to assess the patentee's entitlement to a priority date that precedes the effective date of a reference.

Ex parte re-examination proceedings

The re-examination request is assigned to a patent examiner in the relevant art group who had not earlier been involved in the patent's examination. The examiner must decide, within 3 months, whether the cited art raises a substantial new question of patentability. Under the US PTO's internal standard, the examiner must decide whether there is a substantial likelihood that a reasonable examiner would consider the prior art 'important' in deciding whether or not one or more claims is patentable. This standard is substantially less stringent than that used to reject claims during examination, and the re-examination request is almost invariably granted (almost 95% in 2003).

If re-examination is ordered, the patentee can file an optional statement. This is rarely, if ever, done, because such a response triggers the only formal opportunity for the third-party requester to file an additional paper.

Thereafter, prosecution re-opens and proceeds ex parte (albeit publicly), typically with examination of all claims, to issuance of a re-examination certificate. The certificate either confirms all claims as originally issued (30% of all re-examination certificates issued since 1981 in ex parte re-examinations requested by third parties), cancels all claims (12%) or confirms the patent with amended claims (58%).

Strategic value

Despite its significant limitations, ex parte re-examination offers certain limited advantages to third-party requesters in the face of actual or impending litigation: litigation, with its attendant costs, is typically stayed pending resolution of the re-examination; the burden of proving invalidity is reduced from the “clear and convincing” standard that is required in litigation to “preponderance of the evidence”; and even without invalidation or amendment of the claims, the re-examination proceeding can lead to further statements by the patentee that can be used to limit the construction of the confirmed claims.