Purposive construction

25-05-2008 Print this page
IPPT20041021, UKHL, Kirin Amgen v Hoechst



Purposive construction and article 69 EPC. Person skilled in the art reads [the claim or] the specification on the assumption that its purpose is to both to describe and to demarcate an invention


"33. In the case of a patent specification, the notional addressee is the person skilled in the art. He (or, I say once and for all, she) comes to a reading of the specifi-cation with common general knowledge of the art. And he reads the specification on the assumption that its purpose is to both to describe and to demarcate an in-vention - a practical idea which the patentee has had for a new product or process - and not to be a textbook in mathematics or chemistry or a shopping list of chemi-cals or hardware. It is this insight which lies at the heart of "purposive construction"."


"34. "Purposive construction" does not mean that one is extending or going beyond the definition of the tech-nical matter for which the patentee seeks protection in the claims. The question is always what the person skilled in the art would have understood the patentee to be using the language of the claim to mean. And for this purpose, the language he has chosen is usually of critical importance. The conventions of word meaning and syntax enable us to express our meanings with great accuracy and subtlety and the skilled man will ordinarily assume that the patentee has chosen his lan-guage accordingly. As a number of judges have pointed out, the specification is a unilateral document in words of the patentee's own choosing. Furthermore, the words will usually have been chosen upon skilled advice. The specification is not a document inter rusticos for which broad allowances must be made. On the other hand, it must be recognised that the patentee is trying to de-scribe something which, at any rate in his opinion, is new; which has not existed before and of which there may be no generally accepted definition. There will be occasions upon which it will be obvious to the skilled man that the patentee must in some respect have de-parted from conventional use of language or included in his description of the invention some element which .he did not mean to be essential. But one would not expect that to happen very often."

"47. The Protocol, as I have said, is a Protocol for the construction of article 69 and does not expressly lay down any principle for the construction of claims. It does say what principle should not be followed, namely the old English literalism, but otherwise it says only that one should not go outside the claims. It does how-ever say that the object is to combine a fair protection for the patentee with a reasonable degree of certainty for third parties."


"48. The vast majority of patent specifications are perfectly clear about the extent of the monopoly they claim. Disputes over them never come to court. In borderline cases, however, it does happen that an interpretation which strikes one person as fair and reasonable will strike another as unfair to the pa-tentee or unreasonable for third parties. That degree of uncertainty is inherent in any rule which involves the construction of any document. It afflicts the whole of the law of contract, to say nothing of legislation. In principle it is without remedy, although I shall consider in a moment whether uncertainty can be alleviated by guidelines or a "structured" approach to construction."


Prosecution history

"35. The courts of the United Kingdom, the Netherlands and Germany certainly dis-courage, if they do not actually prohibit, use of the patent office file in aid of construction. There are good reasons: the meaning of the patent should not change according to whether or not the person skilled in the art has access to the file and in any case life is too short for the limited assistance which it can provide. It is howev-er frequently impossible to know without access, not merely to the file but to the private thoughts of the pa-tentee and his advisors as well, what the reason was for some apparently inexplicable limitation in the extent of the monopoly claimed. One possible explanation is that it does not represent what the patentee really meant to say. But another is that he did mean it, for reasons of his own; such as wanting to avoid arguments with the examiners over enablement or prior art and have his patent granted as soon as possible. This feature of the practical life of a patent agent reduces the scope for a conclusion that the patentee could not have meant what the words appear to be saying. It has been suggested that in the absence of any explanation for a restriction in the extent of protection claimed, it should be pre-sumed that there was some good reason between the patentee and the patent office. I do not think that it is sensible to have presumptions about what people must be taken to have meant but a conclusion that they have departed from conventional usage obviously needs some rational basis."


Doctrine of equivalents and article 69 EPC: No need for a doctrine of equivalents – or ‘pith and marrow’ doctrine – if literalism is replaced by purposive construction, which gives a fair protection to the patentee. Article 69 firmly shuts the door on any doctrine which extends protection outside the claims.


"42. If literalism stands in the way of construing patent claims so as to give fair protection to the patentee, there are two things that you can do. One is to adhere to lit-eralism in construing the claims and evolve a doctrine which supplements the claims by extending protection to equivalents. That is what the Americans have done. The other is to abandon literalism. That is what the House of Lords did in the Catnic case, (...).


43. The solution, said Lord Diplock, was to adopt a principle of construction which actually gave effect to what the person skilled in the art would have under-stood the patentee to be claiming."


Equivalence: guidelines for purposive construction

"49. Although article 69 prevents equivalence from extending protection outside the claims, there is no reason why it cannot be an important part of the background of facts known to the skilled man which would affect what he understood the claims to mean. That is no more than common sense.

52. "the Protocol questions" [Improver Corporation v Remington Consumer Products Ltd] have been used by English courts for the past fifteen years as a framework for deciding whether equivalents fall within the scope of the claims. (...). When speaking of the "Catnic principle" it is important to distinguish between, on the one hand, the principle of purposive construction which I have said gives effect to the requirements of the Protocol, and on the other hand, the guidelines for applying that principle to equivalents, which are encapsulated in the Protocol questions.

69. The determination of the extent of protection conferred by a European patent is an examination in which there is only one compulsory question, namely that set by article 69 and its Protocol: what would a person skilled in the art have understood the patentee to have used the language of the claim to mean? Everything else, including the Protocol questions, is only guidance to a judge trying to answer that question.


70. The invention should normally be taken as having been claimed at the same level of generality as that at which it is defined in the claims. It would be unusual for the person skilled in the art to understand a specification to be claiming an invention at a higher level of generality than that chosen by the patentee."


Meaning of “host cell”

"59. (...). The meaning of the term "host cell" is wholly dependent on context. The notion of a host entails the notion of a guest. If the guest is not expressly identified, it must be inferred from context. One answer might have been that the guest was intended to be any DNA whatever. In that case, TKT's human cells are host to the sequences in-serted by homologous recombination. But the judge has held, in my opinion rightly, that "host cell" in the con-text of the specification means "cell which is host to an exogenous DNA sequence encoding for EPO". This is not reading words into the claim any more than when one says that in a particular context "the City" means "the City of London."


New technology

"80. The question is whether the person skilled in the art would understand the description in a way which was sufficiently general to include the new technology. There is no difficulty in principle about construing general terms to include embodiments which were unknown at the time the document was written. […]. It may be clear from the language, context and background that the patentee intended to refer in gen-eral terms to, for example, every way of achieving a certain result, even though he has used language which is in some respects inappropriate in relation to a new way of achieving that result.

84. So perhaps a better answer to the dispute over the second Protocol question is that new technology is another situation in which the Protocol questions may be unhelpful."



"91. The only case in which the EPO will accept a claim to a product defined in terms of its process of manufacture is when the product is new in the sense of being different from any existing product in the state of the art but the difference cannot be de-scribed in chemical or physical terms.

98. The first requirement is that the product must be new and that a difference in the method of manufacturing an identical product does not make it new. It is only if the product is different but the difference cannot in practice be satisfactorily defined by reference to its composition etc that a definition by process of manufacture is al-lowed. The latter may be a rule of practice but the proposition that an identical product made by a new process does not count as new is in my opinion a proposition of law."


Insufficiency claim 19: no enabling disclosure


"109. Before considering any of the four objections, it is, as I indicated earlier, necessary to decide the nature of the invention which the specification had to enable. In my opinion, it was a way of making EPO. […] it was not and could not be the DNA sequence. It could only be a way (however broadly expressed) of making EPO by the use of that information. It could not be EPO itself because that was not new. Nor was it the discovery that a product had a useful quality. The useful qualities of EPO were well known. Even in the case of claims 19 and 26, although they are nominally product claims, the essence of the invention lies in the process. If one keeps in mind that the invention is a way of making EPO, a good deal of the difficulty about sufficiency re-solves itselfIf one keeps in mind that the invention is a way of making EPO, a good deal of the difficulty about sufficiency resolves itself.


126. If the claim says that you must use an acid, and there is nothing in the specification or context to tell you which acid, and the invention will work with some acids but not with others but finding out which ones work will need extensive experiments, then that in my opinion is not merely lack of clarity; it is insufficiency. The lack of clarity does not merely create a fuzzy boundary between that which will work and that which will not. It makes it impossible to work the invention at all until one has found out what ingredient is needed.


129. In the present case, however, the choice of uEPO has nothing to do with making the invention work. It is simply a criterion against which one tests whether the rEPO falls within the claims. The very concepts of "success" or "failure" seems irrelevant to the choice of uEPO. What counts as "success"? Ex hypothesi the skilled person does not know in advance whether any given uEPO will bring his rEPO within the claim or not. From the point of view of success or failure, one is as good as another. All the skilled man can do is try to guess which uEPO the patentee had in mind and if the specification does not tell him, then it is insufficient."

IPPT20041021, UKHL, Kirin Amgen v Hoechst


SESSION 2003-04, [2004] UKHL 46