Poisonous Priority in Patents – A Look at Self-Collision in Europe, Australia, New Zealand, and the USA


In this article, I examine the legal position of poisonous priority in several jurisdictions.


It is hard to believe that self-collision of one’s own patent applications could occur in Europe when Article 88(2) of the European Patent Convention provides:

Multiple priorities may be claimed in respect of a European patent application……. Where appropriate, multiple priorities may be claimed for any one claim…….

Unfortunately, patent proprietors began colliding with their own applications following a decision of the Enlarged Board of Appeal decision (G 2/98) in May 2001. In G 2/98 the Board concluded:

The use of a generic term or formula in a claim for which multiple priorities are claimed in accordance with Article 88(2) second sentence…. is perfectly acceptable……, provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters.

Subsequent restricted interpretation of “clearly defined alternative subject-matters” required a patent claim to explicitly recite alternatives (e.g. apple, banana, pear) falling within the scope of generic term (e.g. fruit).

Self-collision continued to cause problems for patent applicants until July 2015 when the Enlarged Board of Appeal was asked:

Where a claim of a European patent application or patent encompasses alternative subject-matters by virtue of one or more generic expressions or otherwise (generic “OR”-claim), may entitlement to partial priority be refused under the EPC for that claim in respect of alternative subject-matter disclosed (in an enabling manner) for the first time, directly, or at least implicitly, and unambiguously, in the priority document?

The Enlarged Board of Appeal in G 1/15 answered “No” thereby making it much less likely that a generic claim will be refused partial priority overall due to the form of the claim and safeguarding priority entitlement to what is clearly and unambiguously disclosed in the priority document. The decision also provides a cure to poisonous divisional applications.


In Australia, a single claim may be entitled to more than one priority date according to s 43(3) of the Patents Act 1990:

Where a claim defines more than one form of an invention, then, for the purposes of determining the priority date of the claim, it must be treated as if it were a separate claim for each form of the invention that is defined.

Section 43(3) should be effective in avoiding poisonous priority by ensuring claims relying on partial or multiple priorities would not be anticipated by corresponding divisional or parent applications.

However, in AstraZeneca AB v Apotex Pty Ltd [2014] FCAFC 99 the Full Court adopted a similar view to that taken in Europe’s G 2/98 decision. The Court acknowledged that s 43(3) was introduced to permit allocation of different priority dates to “different alternatives comprised in a single claim” but only when the alternatives are explicitly defined:

[251] In our view, claim 1 of the… cation patent does not define more than one form of the invention. Unlike the claim in issue in Thornhill’s Application, claim 1 of the …cation patent does not by its terms allow for any alternatives or, adopting the language of s 43(3), different forms of the same invention. Claim 1 defines only one form of the invention even though there will be any number of potential variants that are within its scope. We do not think s 43(3) is intended to treat every potential variant of the defined invention as if it was a form of the invention that must be treated as a separate claim which is to be given its own priority date. Rather, it is intended to deal with very different situations such as that which arose in Thornhill’s Application or where, to take a slightly different example, a claim is dependent on one or more independent claims (claim 3 of the …cation patent takes this form) each of which has a different priority date.

Despite acknowledging “variants” being encompassed by a claim of the patent, the Court could not relate the variants to more than one form of an invention as required by s 43(3).

New Zealand

According to sections 59 to 62 of the Patents Act 2013, a patent claim may only have a single priority date in New Zealand.

The priority date will be the date upon which all of the subject matter within the claim was first disclosed. In the case of multiple or partial priorities, such as when alternatives are explicitly recited, the priority date of the claim will be the later of the various dates.

With no equivalent to s 43(3) of the Australian Patents Act, poisonous-priority type attacks are more likely to occur in New Zealand than Australia.

Further, poisonous priority is more likely to occur nowadays as the current 2013 Patents Act adopts a “whole of contents” approach meaning text or drawings anywhere in the specification may anticipate a patent claim. Conversely, the previous 1953 Patents Act had a “prior claiming” requirement in which only claimed subject matter could anticipate a claim.


In contrast to the three jurisdictions above, poisonous priority does not appear to have arisen in the USA, most likely due to the legislative provisions in relation to novelty.

Before the America Invents Act was passed, the title 35 U.S.C. 102(e) novelty condition for patentability required novelty destroying prior art to be filed by another entity thereby effectively preventing self-collision:

  • A person shall be entitled to a patent unless-

the invention was described in — (1) an application for patent, published under section 122(b), by another filed in the United States before the invention by the applicant for patent or (2) a patent granted on an application for patent by another filed in the United States before the invention by the applicant for patent,…

In the current legislation, 35 U.S.C. 102(a)(2) continues to avoid self-collision by requiring a prior art document that is relevant to novelty to originate from different inventors:

  • A person shall be entitled to a patent unless-

the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.

An inventor is therefore protected from self-colliding with their own earlier application having the same inventor listing.

The US legislation also helps inventors and companies to evade self-collision scenarios by excluding certain disclosures appearing in earlier applications and patents. Specifically, section 102(b)(2) excludes an earlier application from being cited against a later application under section 102(a)(2) if:

(i) the subject matter in the earlier application was obtained from the inventor (e.g. when a third-party competitor obtains the subject matter from the inventor then quickly files their own application before the inventor can file); or

(ii) the two patent applications are under common ownership or obligation to assign at the time that the later application is filed (e.g. assists a company listing slightly different inventor employees on applications for related inventions as long as the company owns the applications).


Poisonous priority and self-collision remains a potential problem for Australian and New Zealand patent applicants, in particular where applicants file one or more divisional applications and rely on generic terms (e.g. fruit) to cover alternatives (e.g. apple, banana, pear) while failing to explicitly recite each alternative in their patent claims.

If you have any questions about poisonous priority, please do not hesitate to contact us.

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