In 1994, with its landmark decision G 1/93. the EPO's Enlarged Board of Appeal gave birth to the principle of the "inescapable trap": If an application is amended during prosecution with a limitation that is, post-grant, found to be not originally disclosed, and the limitation cannot be replaced without violating the prohibition of post-grant extension of protection, the patent must be revoked. Now, almost 20 years later, patents still regularly die due to this principle, with their innovative value not taken into account at all.
What can you do during prosecution to avoid that your future patents will fall into this trap?
Combine multiple dependent claims only if these are dependent upon each other. For example, when limiting your claim 1 during prosecution with the features of claims 2 and 3, without claims 2 and 3 being dependent upon each other, such an amendment may put your granted patent at high risk. Thus, be mindful of the dependencies when combining claims.
Add features taken from the description literally to the claim. Don't paraphrase. The fact that the Examining Division during prosecution accepts, or even proposes, paraphrased language does not mean that the Opposition Division, or the Board of Appeal, will accept it as well. If they take a different view on the original disclosure, your patent might die. Avoid this risk, and stick to the original wording as well as you can.
Don't add features from the drawings that are not spelled out in the description. Always check for literal support.
Irrespective of the foregoing, the most effective protection against the inescapable trap is an application that is drafted properly according to EPO disclosure practice. This includes having multiple dependencies in the claims, or in corresponding claim-like clauses in the description, and terminology in the description that does not need to be paraphrased or exchanged, when added to the claim.
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