Comparing and Contrasting European 2-part claims with US Jepson claims

EPO member states

Member states of the European Patent Organization.

European 2-part claims and US Jepson claims are similar, but the two claim types are perceived differently on opposite sides of the Atlantic.

Under the European Patent Convention, the claims, whenever appropriate, shall be in the 2-part form, the two parts being separated by the word “characterized”. Many European patent applications are initially written with independent claims in 2-part form, or claims are converted to 2-part during examination.

The Jepson claim is a judicially-recognized claim format in the United States and typically reads :  “A device comprising a, b and c, wherein the improvement comprises d and e.” However, Jepson claims are not fashionable. In his article Patent Claim Drafting: Improvements and Jepson Claims, March 29, 2012, Gene Quinn discussed these claims and why they are out of favor.

EPC Rule 43(1) contains the following definition:

Wherever appropriate, claims shall contain a statement indicating the designation of the subject-matter of the invention and those technical features which are necessary for the definition of the claimed subject matter but which, in combination, form part of the prior art; and a characterizing portion beginning with the expression “characterized in that” or “characterized by” and specifying the technical features which, in combination with the (preamble) features, it is desired to protect.

Strictly speaking it is incorrect to refer to the pre-characterizing part as the “prior art” part. It of course encompasses prior art known in the context of the invention as defined in the designation of the subject matter, however further prior art features known in different contexts can be recited in the claim’s characterizing part.

European practice requires a strict distribution of the features before and after “characterizing”, where those prior art features that are common with the definition of the invention must be included in the pre-characterizing part.  A useful way of thinking about a 2-part claim is that, schematically, the pre-characterizing part, taken alone, is a claim that covers the invention but is so broad that it covers also the closest prior art. This broad definition is followed by a characterizing part that specifies the features that confer novelty to the entire claim. Thus, the pre-characterizing part is is not a definition of the prior art but is a non-novel definition of the invention.


In US law there is no statutory definition of the Jepson claim that corresponds to EPC Rule 43(1). Instead, the Jepson claim is understood from statements in the Ex parte Jepson (1917) decision and in the subsequent case law, summarized in 37 C.F.R. 1.75(e) that recommends a specific template for improvement claims, namely:

(e) Where the nature of the case admits, as in the case of an improvement, any independent claim should contain in the following order:

(1) A preamble comprising a general description of all the elements or steps of the claimed combination which are conventional or known,

(2) A phrase such as “wherein the improvement comprises,” and

(3) Those elements, steps, and/or relationships which constitute that portion of the claimed combination which the applicant considers as the new or improved portion.

US applicants rarely follow this recommendation. What’s more, the Jepson decision specifies:

When an applicant presents a claim, as in this case, which does particularly point out his exact invention, there is certainly nothing in the law to interdict his doing it by including the old parts of the structure in a preamble and set apart from the structure which constitutes the real invention.

This calls for comment. The Jepson format is recognized as a legally acceptable way of claiming, but it seems to be implied that it would be a disadvantageous choice for applicants. The statement also lays a foundation for the perception that the claim preamble is nothing but prior art, and the remainder of the claim is the invention. This thinking has been reinforced over the years by the subsequent case law. Moreover MPEP 2129 specifies:

Drafting a claim in Jepson format … is taken as an implied admission that the subject matter of the preamble is the prior art work of another.

All this leads to the widespread reluctance to use the Jepson format.

Let’s contrast this with the European situation, according to which the invention is defined in the complete claim, whose preamble defines the invention in such broad terms that it encompasses the closest prior art and whose characterizing portion contains novelty-conferring features that may include prior art features from different contexts.

The principle of prior art by the applicant’s admission rather than by publication emerges from G-VII 5.1 of the EPO Guidelines for Examination which states:

In identifying the closest prior art, account should be taken of what the applicant himself acknowledges in his description and claims to be known. Any such acknowledgement of known art should be regarded by the examiner as being correct, unless the applicant states he has made a mistake”.

This allows an applicant to correct an acknowledgement if it was made by mistake, if necessary by amending the description and/or claims. This certainly does not constitute a deterrent for European applicants to make proper use of the 2-part claim format. Of course when a 2-part claim is properly drafted it necessarily encompasses the closest prior art and this is not a point for argument.

Note that PCT Rule 6.3(b) treats 2-part claims divided by “characterizing” and those divided by “wherein the improvement comprises” as equivalent alternatives. Despite presenting the two claim types as alternatives, the PCT has not catalyzed harmonization in the way these claims are interpreted.

Although appropriate use of the 2-part claim is compulsory in Europe, this claim format is popular in Europe mainly because it constitutes a very powerful tool for demonstrating the presence of inventive step in the hands of a drafter who uses it astutely, especially for magnifying small technical differences over the prior art. After all, the closest prior art is an ideal platform for showing off the invention.

The pre-characterizing part of the 2-part claim – which is a generalized (non-novel) definition that broadly covers the invention and the closest corresponding prior art – is not to be equated with the prior art as in US thinking. Instead, the closest prior art should be considered as but one encompassment of the pre-characterizing part. By providing a specific counterpart of the closest prior art in the description, or in arguments in support of inventive step, the drafter can avoid possible misconstruction of the 2-part format.

The 2-part claim is widely used in mechanics and is recommended when the invention is an improvement of a specific piece of prior art.

Over the years, standard situations have been established where the 2-part claim is NOT deemed to be appropriate and therefore a one-part format can be used for European patent applications. This includes: combinations of known integers where the selection of any particular one as starting point would give a distorted view; complex systems of interrelated parts with modifications in several of the parts; modifications of relevant prior art, e.g. omitting features; chemical compounds and compositions; new uses; and inventions where the main prior art is an earlier-filed but later-published European patent application.

There is no longer much controversy over whether or not the 2-part format should be used. If necessary during examination you can change the claim format or reorganize a 2-part claim to comply with an examiner’s request.

Drafters frequently opt to use 1-part claims initially, particularly if they do not have a good knowledge of the state of the art. In all cases, where a 1-part claim is used, the applicant should, if challenged by the EPO examiner, be prepared to justify use of the 1-part format or convert to 2-part.

In drafting 2-part claims for a new patent application, the choice of an appropriate preamble is important because this involves selection of the Field of the Invention, which is critical for classification, search, and determination of the skilled person’s field of knowledge.

As the pre-characterizing clause is part of the claim’s definition of the invention, it is convenient to generalize the definition of the invention in the pre-characterizing part in order to broaden the protection and encompass modifications and variations of the prior art and of the invention.

In the counterpart description in the Background Art it is best to include a specific and non-generalized description of the closest prior art that falls under the generalized preamble. This should encourage the examiner to use the specific prior art as the correct starting point and discourage improperly equating the generalized subject matter of the claim preamble with the prior art. The assessment of inventive step requires a consideration of going from the specific prior art to the invention, not going from the generalized claim preamble to the invention.

The scope of a 2-part claim is defined by the combination of the subject matter of the pre-characterizing part with the subject matter of the characterizing part. Of course, it is important not to include claim limitations in the pre-characterizing part just because they are in the prior art and are not essential for the invention. Such unnecessary limitations create loopholes that can be exploited by competitors seeking to obtain the benefits of the invention while circumventing the claim.

Whether a claim is divided in two parts by “characterized” wording, or is in one part, the scope of the claim is the same. If you replace the characterized phrase by “wherein”, the claim scope remains the same. If the pre-characterizing part is long and the characterizing part is short, the claim scope is the same as if the claim were re-written upside down or with the features divided evenly between the two parts.

By the way, Jepson wording “wherein the improvement comprises” is considered unclear in Europe.

Converting a 2-part claim to 1-part (for example when entering the USPTO) is simple. It suffices to replace the “characterized” word by “wherein”. This does not change the claim scope or its organization and US attorneys who are allergic to the word “characterized” can make this change easily.

On the other hand, converting a 1-part claim to 2-part (for example during EPO examination) is more complicated because you cannot simply randomly insert the word “characterized” but the whole claim structure needs to be reviewed and if necessary reorganized to achieve a correct division taking into account the closest prior art revealed by the search. For this, the European attorney may need to consult with his instructing US counterpart for reshuffling the claim features and to make sure that the pre-characterizing clause properly encapsulates the closest prior art.

In summary, the different perceptions of 2-part claims and Jepson claims have led to the situation where in Europe the 2-part claim is a much-used standard claim format, whereas in the US 1-part claims are favored and the Jepson claim is practically extinct. What has flourished on one side of the Atlantic has perished on the other.

A fuller analysis of European claim drafting practice is given in the 2-volume book Drafting & Amending European Patents available from, key in “patent drafting” or from this link. You have to purchase each volume separately and they will be sent together.


Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of

Join the Discussion

One comment so far.

  • [Avatar for Edward Heller]
    Edward Heller
    December 8, 2016 05:45 pm

    Because the claims alone are published in the local languages of much of Europe, they themselves must inform the reader not only what is the claim covers, but what in the claim is really new.

    In the US, we have grown accustom to claims only providing “some” notice of what is covered without providing any notice at all about what is new. One can ascertain that only by inspection of the file history.

    Moreover, because the Federal Circuit conducts its indefiniteness analysis after construction, US claims generally do not even inform one with any degree of certainty about the scope of the claim. For example, if a functional claim element refers to novel structure or methods described in the specification, the claim itself neither describes the novel subject matter nor the scope of protection.

    There is little wonder why so many in industry complain about patents being asserted against them. Given degree of obfuscation permitted by the Federal Circuit and by 112(f), the main effort of practitioners in drafting is to generalize, to obscure, to fail to be specific at all. This effort is judged by both firm and client alike as good practice. But it does not make for a good patent system.

    We should learn what we can from the Europeans here.