A European patent may be opposed within 9 months of it being granted.  The opposition is a centralised procedure, handled by the European Patent Office, but the result of the opposition has effect in all countries designated in the European patent.  If an opposition is successful, the European patent may be maintained but in an amended form or, worse, revoked.

An opposition may be filed on the grounds specified in Article 100 EPC:

• that the subject-matter of the patent is not patentable within the terms of Articles 52-57 EPC, typically that the patent lacks novelty and/or an inventive step,
• that the invention is not disclosed clearly and completely enough for a person skilled in the art to carry it out,
• that the patent’s subject-matter extends beyond the content of the application as filed.

The following tips can help ensure your European patent is in a good position to defend a possible opposition.

1. Include commercial embodiments in your claims

Often, commercial embodiments are narrower in scope than embodiments of the invention that you wish to protect and have set out to protect when drafting the patent application.  However, these narrower, commercial embodiments specifically cover the product or process etc which is of particular commercial value.

During opposition proceedings, it is a lot easier to limit an independent claim to features found in a dependent claim rather than extract features from the description to cobble together an amended independent claim.  Taking features from the description also increases the risk of added matter objections being raised against an amended claim.  Having commercial embodiments specifically claimed in dependent claims helps to ensure commercial interests are protected.

2. Avoid being caught in an inescapable Art. 123(2)/(3) trap

Article 123(2) of the European Patent Convention states that “The European patent application or patent may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed”.  During prosecution of a patent application, the claims, which define the scope of protection sought, of the application may need to be amended to overcome objections raised by the patent Examiner.

The content of an amended claim in a patent application must be directly and unambiguously derivable from the application as filed.  However, if this is not the case, and an amended claim defines subject matter which is not directly and unambiguously derivable from the application as filed, the claim is likely going to be objected to by a patent Examiner on the basis that it contravenes Art. 123(2) EPC.

Once a European patent is granted it is not possible to amend it in such a way as to extend the protection it confers (Art. 123(3) EPC).  This becomes a problem in the event that a limiting amendment introduced during prosecution is found, after grant (e.g., in opposition proceedings), to add subject matter beyond the content of the application as filed in contravention of Art. 123(2) EPC.  The patent owner may then find themselves in an inescapable Art. 123(2)/(3) trap.

Removing this limiting feature would broaden the claim after grant, which is not allowable under Art. 123(3) EPC.  Thus, you are left with a claim which adds subject matter and is, therefore, likely to be deemed unallowable during an opposition, yet the feature which adds subject matter cannot be removed from the claim, as this would broaden the claim scope (contravening Art. 123(3) EPC).

So, when making amendments to the claims during prosecution before grant, it is important to not include any feature in an independent claim which has questionable basis in the application as filed.  If a feature with questionable basis in the application as filed is likely to result in an allowable claim, it is tempting to include this feature in an independent claim, and an Examiner may even suggest such an amendment, unaware of the possible issues that may arise post-grant.  However, if there is any doubt regarding the basis for an amendment to an independent claim, err on the side of caution and don’t make the amendment.

3. Dependent claims include clarity-immune subject matter

Clarity cannot be challenged in an opposition unless amendments to the claims are made using features found only in the description.  Thus, any subject matter found in dependent claims is immune from an objection based on lack of clarity if the subject matter of the dependent claims is incorporated into independent claim 1 during opposition.

As such, it is very useful to have subject matter in dependent claims, rather than only in the description, when a patent is granted if such subject matter is considered to provide a good fall-back position in the event of an opposition.

4. Check for claim errors and potentially unclear language at the Intention to Grant (R. 71(3)) stage

In opposition proceedings, any errors or issues with claim language can be an unnecessary distraction and can provide your opponent with further ammunition with which to attack your patent.

Even if an amendment seems trivial, any errors in claim dependencies and antecedent basis should be corrected in response to an Intention to Grant communication under R. 71(3) EPC as it is not possible to correct these errors during opposition unless it is specifically in response to an objection raised during the opposition.

It is important to check for errors made by the patent Examiner during prosecution.  In particular, it is common for patent Examiners to make amendments to the claims and description when issuing an Intention to Grant communication under Rule 71(3) EPC.  Such amendments are made with good intentions to correct relatively minor deficiencies in the claims and/or description without the need to issue a formal examination report.  However, such amendments must be carefully checked by the applicant and/or their representative to ensure that the Examiner has not made a careless error.  For example, any Examiner-made amendments to the claims must be checked to ensure that the amendment has not put the claim(s) into an inescapable Art. 123(2)/(3) trap, as outlined above.  Just because an amendment has been made, or suggested, by the patent Examiner, does not mean it is immune from objection post-grant, e.g., during opposition proceedings.

5. File a precautionary divisional application before grant

If there is concern that your patent may be opposed, a sensible strategy is to file a precautionary divisional application to try and cover broader subject matter than was able to be covered in the parent (opposed) patent, or to try and cover specific, commercially relevant subject matter.

In addition, the objections raised against the parent case, either during examination or opposition, can be considered when filing and prosecuting the divisional application to obtain stronger protection than in the parent patent.  A divisional application may also prove extremely useful if the parent patent becomes caught in an Art. 123(2)/(3) trap during opposition.

If you would like advice preparing your European patent, please get in touch to speak to one of our attorneys.