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In construing a specification, a court will accept expert evidence as to the technical matter involved (i.e. it will put itself in the position of the addressee), but having done so will decide on its own construction - the court will not take evidence as to the proper construction (see Simpson v Holliday (1866) L.R., 1 H.L. 315 and also quoted in Vidal Dyes v Levinstein (1912) 29 RPC 245).

Blanco White, Fifth Edition, 2-101, states:

"As with any other document, questions of construction of a patent specification, arising in legal proceedings, are for the court to decide as a matter of law; for this purpose the court must first instruct itself as to the technical matters involved, so as to place itself in the position of one acquainted with the art concerned - in the position, that is, of a person to whom the specification is addressed. The document must in particular be read with the skilled addressee's understanding of what the inventor is trying to achieve and his appreciation of what is important, what is not. Given the necessary knowledge and understanding, however, the question is (we are told) what the words of the document mean, not what information a man skilled in the art would in fact derive from them; and expert evidence as to their meaning is in general not admissible."

Examiners should take a similar approach, however their own technical background substitutes for expert evidence. Thus, it is ultimately for examiners to decide what construction to place on a specification and likewise for documents that are being cited for anticipation purposes (see also 2.4.5.Construing the Citation).

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