The Full Court found no infringement based on its construction of the claims. Emmett J set out the law as follows
It is for the Court to construe the language of the claims.
The principles guiding construction are not significantly different from those applicable to the construction of any other written instrument.
Ordinary words should be given their ordinary meaning unless a person skilled in the relevant art would, in the context of the claims, give a special meaning or unless the complete specification ascribes a special meaning to the words of the claim.
Expert evidence may be given in support of a claim that a word has a technical meaning.
However, in the absence of a special technical meaning, expert evidence is not determinative of the construction of the claims.
As meaning may vary with context, it is necessary, with any question of construction, to read the whole of the relevant instrument, whether or not there is any apparent ambiguity in the language to be construed.
Ultimately, however, it is the claims that are to be construed, and the context provided by the complete specification cannot limit, vary or qualify the clear meaning of the claims.
The author of a document such as a patent specification uses language to make a communication for a practical purpose.
A rule of construction that gives that language a meaning differing from how that language would have been understood by the persons to whom it is addressed is liable to defeat the author’s intentions.
Thus, a patent specification should be given a purposive construction rather than a purely literal one derived from applying to it a meticulous verbal analysis.
Construction of a patent is not subjectively concerned with what the author meant to say.
Rather, it is objective, in the sense that it is concerned with what a reasonable person to whom the patent is addressed would have understood the author to be using the words to mean
17).
The notional addressee of a patent is a person skilled in the art to which the patent relates.
That person comes to a reading of the specification with common general knowledge of the art, and reads the specification on the assumption that its purpose is both to describe and to demarcate an invention.
The purpose of a patent specification is simply to communicate the idea of an invention.
An appreciation of that purpose is part of the material that is used to ascertain the meaning.
However, purpose and meaning are different.
Purposive construction does not mean that one is extending or going beyond the definition of the technical matter for which the patentee seeks protection in the claims.
The question is what a person skilled in the art would have understood the patentee to be using the language of the claim to mean.
Accordingly, for that purpose, the language chosen is of critical importance.
The specification is a document in words of the patentee’s own choosing, which will usually have been chosen upon skilled advice
18)