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The threat of poisonous divisional attacks at the European
Patent Office has been creating uncertainty for some years.
The February 2017 reasoned decision of the EPO's Enlarged Board of
Appeal in G1/15 offers welcome respite. In summary, whilst
this decision does not directly address the question of whether or
not a divisional application can be cited against its parent (or
vice versa), if we follow the reasoning in the decision, the
concept of a "poisonous divisional" necessarily disappears. This
decision will be a strong tool to dispose of poisonous divisional
The decision relates first and foremost to the issue of "partial
priorities", i.e. whether a single claim can comprise
subject-matter with different effective dates. This would generally
occur where the claim is broader than the disclosure of the
Previously, it was thought that if a claim is not directed to
"clear alternatives" (e.g. A or B) then the whole claim would lose
its priority entitlement if only one alternative was disclosed in
the priority document. This commonly occurred when a claim included
continuous numerical ranges or Markush formulae in
The crux of this decision is that a claim may be "conceptually"
divided into two parts, i.e. that which has a valid claim to
priority because the subject-matter is disclosed in the priority
document, and that which does not. Thus, even if the claim is not
directed to clear alternatives by use of the word "or" or similar,
it may still have partial priority. For instance, where the claim
is directed to a numerical range (1-10), and only part of this
range is disclosed in the priority document (e.g. 1-4), the range
may be conceptually divided into two parts (e.g. 1-4 and 5-10),
where the first part of the range has valid priority but the second
part does not.
Relevance of the decision to a poisonous
The decision stops short of then applying this reasoning to a
so-called "poisonous divisional" scenario. The fundamental question
of whether a divisional can be cited against its parent, or vice
versa was not considered. However, following the logic of the
decision it appears that this decision may bring an end to the
poisonous divisional issue in some circumstances.
In the above scenario, if a divisional application were filed it
would necessarily have the same disclosure as the parent (i.e. it
would disclose the range 1-10). As the divisional takes the same
filing date as the parent, and claims the same priority, the same
logic should apply. In other words, the range disclosed in the
divisional application may also be conceptually divided, as it was
in the parent claims, so that part of the range is entitled to
priority, and part of it is not. If this is the case then the
subject-matter of the divisional will always have the
same effective date as the same subject-matter in the parent
application and neither can be prior art against the other.
However, this favourable interpretation depends on how you apply
Article 54(3) EPC, which states that European patent applications
having a filing or priority date prior to the effective date of the
claimed subject-matter, and a publication date afterwards, are
citable against the claim for novelty (not inventive step).
The question is whether or not a divisional application may be such
an Art. 54(3) EPC application. Specifically, this comes down to
whether you adopt a "whole contents" interpretation, or a "same
subject-matter" interpretation of Article 54(3) EPC.
The above favourable interpretation employs the "same
subject-matter" interpretation, which complies with the Guidelines
G,5.1.1:"If the published European patent application [claims
priority, the priority date replaces the filing date for
that subject-matter in the application which corresponds to the
Applying these Guidelines, the 54(3) application may also be
divided into parts which validly claim priority and parts which
don't. It follows logically that only those parts of the 54(3)
document which validly claim priority can be citeable against a
later application, and then those parts are only citable against
subject-matter within the later application which has a later
effective date. Since the subject-matter disclosed in a divisional
will always have the same effective date as the same subject-matter
in the parent it seems would seem impossible for a divisional to be
cited against its parent.
Note that this does not preclude a "toxic priority"
problem where a priority application has a narrower disclosure than
the priority claiming application and is published before the
filing date of the priority claiming application.
The "whole contents" interpretation, on the other hand, suggests
that the whole of the disclosure of a 54(3) document is citeable
against the claimed subject-matter if the claimed subject-matter is
not entitled to priority, regardless of whether or not
the specific subject-matter within the divisional application
which is being cited against the claim is actually entitled to
priority. This comes from a literal interpretation of The
Guidelines G, 5.1, which states that "By the "content" of a
European application [referring back to Art. 54(3) EPC"] it is
meant the whole disclosure, i.e. the description, drawings and
This "whole contents" approach seems inconsistent with this new
decision which advocates conceptually carving up a claim or
application into parts which do, and parts which do not claim
priority (see especially reasons point 5.1.2).
Thus, whilst this decision does not directly address the
poisonous divisional problem, it goes some way to addressing it if
we follow the overarching logic of the decision.
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