On 2 June 2014, the US Supreme Court issued its decision in Nautilus, Inc. v BioSig Instruments, Inc., 572 U.S. __ (2014), No. 13-369, resurrecting an issue at the heart of patent claim language: what constitutes indefiniteness? In other words, how much ambiguity is too much ambiguity in a claim? This case has brought to light the importance of concise claim language and the ramifications of ambiguous claim language. This case serves as a useful reminder that Applicants must be cognisant of definite claim language, not only in the United States, but in Canada and Europe as well.

In the United States, whether claim language is the hot topic during prosecution of a patent application or during litigation of an issued patent, the statute of relevance is 35 USC §112(b). However it is generally accepted that the statue is applied differently for pre-issuance claims and issued claims.

According to the Federal Circuit, claim language cannot be 'insolubly ambiguous'. This threshold has now been revised by Nautilus when the Supreme Court adopted the threshold of "reasonable certainty".

At the United States Patent and Trademark Office (USPTO), a different standard for indefiniteness is used, arguably for a number of reasons. First, examiners are required to construe claim language using the broadest reasonable interpretation. The key word there of course is the word "reasonable", indicating a fair and sound interpretation.

Second, the patent applicant has the opportunity to amend claim language in view of the examiner's comments. This is a luxury afforded only during prosecution of pre-issuance claims.

Third, the examiner does not enjoy the benefit of referring to the prosecution history since it is a document in progress. In contrast, in court, claims are construed in light of the prosecution history.

USPTO guidelines mandate a three step process in determining definiteness. Step one has the examiner interpreting the claims. This is done in context with the specification. The second step has the examiner determining if the claim language is definite; for example, indefiniteness arises when two or more plausible interpretations of the claim language exist. The third step is to resolve the indefiniteness problem. The examiner must put forth a prima facie case of indefiniteness. The burden then shifts to the applicant to rebut the prima facie case; this could be done by providing an explanation or definition for the indefinite language or by amending the indefinite language.

In Canada, claim language is construed against the requirements of the Canadian Patent Act and Patent Rules using purposive construction. Under Section 27(4) of the Canadian Patent Act, a claim is considered definite if a person ordinarily skilled in the art would understand its intended scope.

In response to, and consistent with, the Federal Court of Appeal decision (Attorney General v Amazon.com Inc. 2011 FCA 328), the Canadian Intellectual Property Office (CIPO) released practice notices providing guidance to Examiners on how to construe claims. You can read more about these practice notices in our previous article.

Interestingly though, claim construction guidelines (PN 2013-02) seem to imply that different principles of claim construction apply at CIPO than at the courts. In particular, “self-inflicted” wounds caused by an Applicant’s own action that adversely affect claim construction are not considered applicable during prosecution. In a similar fashion to principles applied in the US, this is because claim language is fluid during examination.

The Federal Court of Canada (FCC) holds a threshold that claims must not be “avoidably ambiguous” (Pfizer Canada Inc. v Canada (Minister of Health), [2005] F.C. No. 1725 (Federal Court of Canada 2005)). The FCC has held that a claim will be invalidated if the language is avoidably ambiguous due to carelessness or want of skill. However, the FCC specifically holds for allowances in defects in the case of inventions that are difficult to explain. By protecting the acceptance that some difficult claim language is permissible, the FCC has an arguably lower threshold of claim indefiniteness than the United States.

In Europe, the statute of interest is Article 84 of the European Patent Convention. Under Article 84, claims must be clear and concise. The European Patent Office has published Guidelines for the Examination in the European Patent Office, 1994 (revised in 1995). The Guidelines in Part C, Chapter III, 4.2 require that claim language be given the meaning and scope normally used in the relevant art. At first blush, it seems that this is different from the generally accepted principle that Applicants are free to be their own lexicographer in the United States. However, the same provision also seems to permit some latitude in claim construction by accepting a departure from strict literal interpretation of claim language.

Article 69 of the EPC provides further support that claims should not be interpreted using a strict literal approach, but that a “fair” approach should be taken.

Lack of clarity is of importance during prosecution of claims in Europe, just as in Canada and the United States. In contrast though, lack of clarity is not a ground for opposition or revocation of the European patent.

What does all this mean for the patent drafter writing new applications or prosecuting pending applications? Practitioners must remain vigilant while drafting patent applications and should conduct a thorough review of claim language with a view towards definiteness. Claim language should be studied in context with the specification for consistency. It will be important to ensure there is adequate support for all claim elements, subjective language and terms of degree. Functional language should have sufficient structure in the specification and all alternatives should be identified and defined.

Jurisdictional differences must also be considered and appropriate amendments be introduced during prosecution of claims in Canada, the United States and Europe. For example, optional features in a claim are permissible in Europe if they do not introduce ambiguity, but will be expressly objected to in Canada. Reference signs matching claim elements to elements in the drawings can be used in improve claim clarity without limited claim scope in Europe; in contrast, reference numbers in claims in Canada may adversely affect determined claim scope. In the United States, means-plus-function clauses can prove problematic while the same recitation in Canada may be used to broaden claim scope without deterring from claim clarity.

Some practitioners believe that Nautilus has increased the patent drafter's burden in the United States, while some believe that the court has left room for inherent claim limitations and some degree of interpretation. Either way, practitioners should take the case as a reminder that claim definiteness is an issue not to be overlooked in any jurisdiction. Patent applicants should look to local representation to counsel on appropriate claim language to maximise claim breadth while maintaining claim clarity.