IPKAT GUEST BLOGGER OF THE MONTH

Each month Ipkat invites a prominent member of the intellectual property community to contribute a guest blog. Our first guest blogger is London-based barrister Ashley W. Roughton of Hogarth Chambers. Ashley’s practice covers a wide variety of IP topics and he is a co-author of The Modern Law of Trade Marks. He has recently appeared in Arsenal v Reed. Ashley’s chosen subject is file wrapper estoppel, a US legal concept which is being spoken of in UK courts with increasing frequency. If you have any comments on Ashley’s guest blog, please mail them to us at theipkat@yahoo.co.uk.

File wrapper estoppel (where a patent applicant is absolutely bound by representations made to the Patent Office) is unknown in the UK. However it seems wrong that an applicant can get his patent by telling the Patent Office that his patent specification or claims mean one thing and later tell the court something quite different in order to catch an alleged infringer. How much, asks the law, can this sort of behaviour enlarge the defendant’s rights? In the UK the answer is not at all: it is not the defendant’s rights which are enlarged but those of the claimant which are diminished. A patent claim not drafted in good faith and in need of a narrowing amendment may not be amended without the discretionary permission of the court, which takes into account, among other things, shifts in the applicant’s position. But at trial the applicant is not held to his representations to the Patent Office. There is some sense in this: if file wrapper estoppel becomes a UK doctrine, the overall patent specification essentially comprises the finally granted claims and specification as well as the Patent Office file held in Newport and, possibly, any oral representations which can be established in evidence. So instead of having one document to seek and construe, you have two and perhaps some hearsay. The Comptroller is not obliged to maintain her files but just to maintain the register.

Imagine now that the CEO of Largeco, a pharmaceutical company, announces that "our latest patent will stop nobody producing pain killers containing proprionic acid derivatives". Smallco produces a proprionic acid derivative pain killer and Largeco sues. Smallco argues that (i) what the CEO said is a public statement that strict legal rights will not be enforced, which Smallco relied upon to its detriment (a classic estoppel situation) and (ii) that what the CEO said amounts to a licence. The second argument is difficult because a bare licence can be withdrawn on reasonable notice, say 6 months, when Smallco wants to produce. The first defence is, however, upheld. Plenty of authorities support this proposition and many defences have succeeded along these lines, though UK courts will not construe a patent’s claims and specifications by reference to what others say about it - even if those others own it.

Now, what is the difference between the CEO making his statement public or writing it down on paper and depositing it in a publicly accessible Patent Office file? Superficially the answer seems to be none, though UK law might not regard this as estoppel unless Smallco shows it read that document before it embarked upon production. Estoppel arises because what is said is simply a statement that Largeco will not insist upon its strict legal rights ― but it must be clear and unequivocal and it must be intended that Smallco will act upon it. The difference between this and file wrapper estoppel is huge. The latter imposes no apparent requirement of reliance ― the doctrine can be relied upon even if the prosecution file was not read before the infringing acts took place.

Do we need file wrapper estoppel in the UK? Mr Justice Jacob in the recently reported Celltech Chiroscience case justifiably advises caution. The European prosecution file would be in any one of three languages and, if US experience is anything to go by, many US patent infringement proceedings are taken up with arguments about what the prosecution file actually meant. Conversely UK courts have faced little real criticism of the way they construe patent claims and specifications.