The need to control costs in jurisdictions where government fees increase substantially based on the number of claims often forces patent practitioners to use various claim drafting strategies, including multiple dependent claims.
However, multiple dependent claims must be drafted carefully, as there is a risk that they could be considered unclear or contain features which are inconsistent with those of the claims on which they are based.
Multiple dependency and definition of 'features'
The main focus when examining a set of claims in regard to dependence should not be verifying whether there are multiple dependent claims per se, but rather whether the dependent claims are clear. Multiple dependent claims will often be inconsistent (eg, they may define two embodiments of corresponding features which are incompatible). It is also important to analyse the wording of multiple dependent claims, as they will be interpreted differently depending on whether the list of claims ends with "or", "and" or "and/or". For instance:
- An invention comprising…
- The invention of Claim 1 further comprising Feature 1 and Feature 2.
- The invention of Claim 1 further comprising Feature 3 and Feature 4.
- The invention of Claims 2 or 3 further comprising a sub-feature of Feature 2.
- The invention of Claims 2 and 3 further comprising a sub-feature of Feature 3. (Emphasis added.)
When assessing the dependence of Claim 4, an examiner should verify whether the features defined therein are consistent with both Claims 2 and 3. This is because the word "or" implies that what is claimed in Claim 4 can include only the features of Claim 2 or only the features of Claim 3. In the above example, Claim 4 is inconsistent with the features of Claim 3 because a sub-feature of Feature 2 would be unclear since Feature 2 has not been defined in the whole dependency chain (ie, Claims 1, 2 and 4). In other words, Claim 4 includes so-called 'impossible embodiments', as the sub-feature of Feature 2 is interpreted under the restrictions of Claim 3 because only Features 3 and 4 are present in its definition.
Conversely, as regards Claim 5, it would be sufficient for the features defined therein to be consistent with the features defined in either Claim 2 or 3, as the word "and" implies that Claim 5 must include the features of both claims. In other words, because Claim 5 needs the presence of both Claims 2 and 3:
- Feature 3 is present in any embodiment defined in Claim 5; and
- therefore, a sub-feature of Feature 3 would be consistent.
The most common practice for reducing claims in a given application is cumulative dependency, an example of which is as follows:
- An invention comprising…
- The invention of Claim 1, further comprising Feature 2.
- The invention of any of Claims 1 or 2, further comprising Feature 3.
- The invention of any of Claims 1 to 3, further comprising a sub-feature of Feature 2.
- The invention of any of Claims 1 to 4, further comprising a sub-feature of Feature 3.
Cumulative claiming leads to inconsistency with regard to Claims 4 and 5. This is because Claim 4 may or may not comprise Feature 2, as Feature 2 is optional in Claim 3. As such, Claim 3 comprises embodiments in which only the features of Claim 1 or Feature 3 are present. Likewise, Claim 5 includes embodiments where:
- only features of Claim 1 are claimed with a sub-feature of Feature 3; or
- only the features of Claim 1 and Feature 2 (with or without Sub-feature 2) are claimed, thus rendering the claim inconsistent and therefore unclear.
Parties skilled in the art may understand that impossible embodiments should not be considered within the scope of a multiple dependent claim, and that this practice promotes another characteristic of claims: conciseness. This situation is common but undesirable in a litigation setting, where the clarity of a claim will be questioned and which, in the international context of patent prosecution, may have different consequences from country to country.
This is particularly true when the scope of an independent claim is restricted by adding a feature of a dependent claim. This kind of inconsistency is often automatically introduced when a feature included in a new independent claim is not verified for consistency, which is harder to detect with cumulative dependent claims.
Article 47, Fraction III of the Industrial Property Law reads as follows:
Article 47.- A patent application shall be accompanied by:
III. One or more claims, which shall be clear and concise and shall not exceed the contents of the description."
The Regulations of the Industrial Property Law include further rules for claims, under which multiple dependent claims are permitted, with certain restrictions. The last two paragraphs of Article 29, Fraction VI of the regulations govern dependent and multiple dependent claims as follows:
Dependent claims shall comprise all the features of the claims from which they depend and shall precise the additional features that maintain a consistent relationship with the related independent or dependent claims. Those claims depending on two or more claims shall not serve as a base to any other claim that is in turn dependent on two or more claims.
Mexican law is very specific with regard to multiple dependencies. According to the above article of the regulations, a multiple dependent claim cannot be the basis of another multiple dependent claim. However, in practice, this provision is not always followed and most Mexican examiners commonly accept multiple dependent claims with the type of cumulative claiming shown above.
In the above example of cumulative claiming, if the examiners analysed these claims filed in a patent application according to Article 29, Fraction VI of the Regulations of the Industrial Property Law, Claims 1 to 3 would be fully acceptable in regard to dependence. Claim 1 is independent, Claim 2 is dependent only on Claim 1 and Claim 3 is multiply dependent on Claims 1 and 2. Assuming that the features were consistent, Claims 1 to 2 would be in good standing. However, Claim 3, a multiple dependent claim, serves as the basis of another multiple dependent claim, Claim 4, which in turn refers to Claims 1, 2 and 3. Accordingly, Mexican examiners should not accept Claims 4 and 5 because they do not comply with Article 29, Fraction VI of the Regulations of the Industrial Property Law. Claim 4 would be acceptable if it referred only to Claim 3.
The main concern of Mexican examiners when examining a set of claims with regard to dependence is not verifying whether there are multiple dependent claims, but rather whether such claims are clear.
Multiple dependent claims must be drafted carefully. For important inventions, the risk of rendering a claim unclear due to inconsistencies between multiple dependent claims is not worth the risk. Mexican law is fairly clear in this regard, as it establishes that multiple dependent claims are permissible if they are clear and do not serve as the basis of another multiple dependent claim.
As such, even though Mexican examiners may accept cumulative dependent claims, they should be avoided where possible to prevent unnecessary requirements being imposed by the examiners, which could lead to delays in prosecution and ultimately to the invalidity of the claims. Notably, the above observations are based only on the clarity requirement and not other requirements which may be relevant when multiple dependent claims are used to restrict the scope of broad independent claims during prosecution, such as novelty, inventive step and industrial applicability.
For further information on this topic please contact Héctor Elias Chagoya at Becerril, Coca & Becerril SC by telephone (+52 55 5263 8730) or email ([email protected]). The Becerril, Coca & Becerril website can be accessed at www.bcb.com.mx.
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