Added Matter (1) - Direct and unambiguous

Probably the most infamous feature of the EPO is the added matter rule. Frequently met with cries of derision and panic, it has been the downfall of many wonderfully clever inventions. A strong understanding of the EPO's approach to added matter is critical for not only prosecution, but also for drafting applications that may later be examined by the EPO. Since the same rules apply to a priority claim, it is also important that priority-founding applications are drafted with the same rules in mind.

The EPO’s Enlarged Board of Appeal, which is tasked with ensuring uniform application of European patent law, have termed the EPO's approach the "gold standard", which is a nice glossy phrase, but doesn't really help understand it. Somewhat more useful is the commonly stated "direct and unambiguous" test, which I think is the best route to understanding whether an amendment has basis under the EPO’s standards. Although usually used in a negative sense "there is no direct and unambiguous disclosure", the test can also be used in a positive sense to convince examiners "there is direct and unambiguous disclosure because …". The two parts of the test are closely linked and must both be considered when assessing an amendment.

The first part of the test, "direct", relates to how closely the amendment is related to its source and whether a step is needed between the basis and amendment. An amendment which is disclosed verbatim is clearly directly disclosed (provided the verbatim text is in the right context, more on that in future instalments of this series), but verbatim basis is not necessarily required and where there are differences in the text it must be assessed whether the basis is still direct.

For example, if we have a description of a bicycle which does not mention the number of wheels, do we have basis for an amendment to specify a human-powered vehicle with two wheels? The amendment is not disclosed verbatim, but is there “direct” basis? On one hand, no, because there is no mention of two wheels, but on the other hand does a “bicycle” implicitly disclose two wheels? An important element of the direct part of the test is that it is applied based on what a Skilled Person would understand based on their Common General Knowledge. It is likely that the Skilled Person would understand a bicycle always has two wheels and hence there would be direct basis for a human-powered vehicle with two wheels. However, if the desired amendment was “a vehicle with two wheels”, the test is unlikely to be met because that would include a motorbike, which the same Skilled Person would not arrive at directly from “bicycle”.

Turning to "unambiguous", this tests how specific the disclosure is in relation to the amendment - if the reader has more than one possible choice (each of which is technically reasonable), then the disclosure may be ambiguous. For example, disclosure of a "silver-coloured precious metal" is unlikely to provide basis for an amendment to “the metal is silver” because it is ambiguous whether it is a reference to silver or platinum.

It is worth noting that although we primarily focus on the claims, the same rules apply to the description and figures. Any amendments there require the same basis and so even small “tweaks” to the description or figures should be carefully considered. It is often better to leave small clarity issues or errors alone rather than run the risk of inadvertently introducing an added matter problem.

Application of the rules is of course complex, and very dependent on the specifics of each case, but there are a number of categories of amendments to which more general rules can be applied. We will explore those over the coming weeks.

The key takeaway is that when drafting, or making amendments, you should think carefully about the scope and meaning of the words you are using, and whether they lead the reader to the claim scope you wish to achieve. During drafting this means making sure your language provides you the basis for later possible amendments, when considered against the direct and unambiguous rule. During examination this means ensuring your amendments accurately fit the basis you have and that you argue for them as being "direct and unambiguous".

Coming next - The inescapable trap; why a bad amendment can kill a patent.

This article is a part of our EPO Practice and Peculiarities series. Click here to explore.