Consider plausibility when drafting your European patent

In order to be granted, or found valid during court proceedings, a European patent application or patent must be novel, inventive, and sufficiently disclosed that the claimed invention can be carried out by a person skilled in the art.

When considering these issues, the examiner or court may bring the issue of plausibility into play. While not a ground for refusal or invalidity in itself, it can be used as a standard by which another criterion (most commonly inventive step or sufficiency) is assessed.

Plausibility relates to whether, at the time of filing, the claimed invention was credible, and its consideration is intended to prevent purely speculative applications: it must be at least credible that the claimed invention demonstrates the disclosed technical effect. It is particularly relevant to chemical and pharmaceutical applications, where the link between a technical feature and its technical effect is not self-evident or may be unpredictable.

While the bar for plausibility, that the invention is “credible”, is low, falling foul of it can cause real problems for an application as it is assessed as at the filing date: the application as filed must be plausible. In essence, the application as filed must demonstrate that the applicant was in possession of the claimed invention at the filing date.

Despite this, there are a number of ways in which a plausibility objection may be addressed, depending on the nature of the particular objection:

• While an application must be plausible at the date of filing, inventive step may be supported by post-filed data. When plausibility is linked to an inventive step objection, it is sometimes possible to address the inventive step objection by submitting post-filed data, and to simultaneously overcome the plausibility objection. However, as sufficiency is also assessed as at the date of filing, where a plausibility objection is linked to a sufficiency objection then post-filed data will not be accepted.


• Where the application contains appropriate fall-back positions, it may be possible to narrow the scope of the claims to reflect the subject-matter for which evidence is provided in the specification (or to represent a reasonable extrapolation from that data).


• Where the common general knowledge at the time of filing would render the subject-matter credible (but not obvious), then it may be possible to submit evidence of this to overcome the objection. Prior art documents, particularly those cited in the background of the patent/application to demonstrate the state of the art, may be used as evidence.

Nevertheless, the best time to avoid a plausibility objection is at the drafting stage. Drafting tips for avoiding plausibility objections include:

• Ensure that at least some evidence and/or data is provided in the specification to support the claimed invention.


• Provide intermediate fall-back positions in the general description and/or claims which focus on the subject-matter for which data is provided, to provide clear basis for later amendment.


• Include references to relevant prior art documents, and/or a clear description of the common general knowledge at the time of filing, in the background section of the application.


• Ensure that all embodiments are consistent with the data/evidence provided.


• Where the technical disclosure follows accepted knowledge, then the requirement for evidence may be lower as plausibility will be supported by the common general knowledge. Where the technical knowledge goes against the accepted knowledge, or breaks into entirely new ground, then the requirement for evidence will be greater.

Plausibility is an important criterion to have in mind during drafting as, if the application as a whole is considered implausible, there is no data provided on which to rely, or the only options for amendment to a credible invention are too narrow to be of use to the applicant, then a plausibility objection may prove fatal to an application.