All IP practitioners are aware of the importance of expert evidence in patent proceedings in the English courts. Lengthy cross examination requires a party to select witnesses with the relevant knowledge, but also with the ability to express their own views even under the most rigorous questioning. Care must, of course, be taken when instructing an expert how to prepare his evidence. The importance of this topic has been highlighted by Mr Justice Arnold in his recent decision in the MedImmune v Novartis1 case. It was of such importance that Arnold J. devoted no fewer than 58 paragraphs of his judgment to expert evidence.

A key feature of English litigation is that experts have a primary duty to the Court, not to the party by whom they are retained. Arnold J. was keen to emphasise that the opinion given by an expert must be independent and impartial and the responsibility for the impartiality of the report is shared between the expert himself and the lawyers instructing him. Lawyers instructing experts have a duty to explain the expert’s responsibilities, which extends beyond merely drawing the expert’s attention to the relevant sections of the Civil Procedure Rules. Whilst Arnold J. did not criticise the practice of lawyers drafting expert reports on the basis of what the expert has told them, he did note that the responsibility to ensure that the report is objective falls squarely upon the shoulders of the lawyer. To ensure impartiality, the expert report should not focus solely on the aspects of documents supporting one party’s case, but should give a balanced interpretation of the documents. Similarly, if the expert has given evidence on the same or similar subject matter before other courts or patent offices, this should be explained in his evidence, together with any publications the expert has authored in the field. As the Judge explained, the party’s opponent will, of course, scour the expert’s publication history and, if these matters are not dealt with in evidence, the lawyers run the risk that the evidence is discredited, harming both the expert, and their client’s case.

Another fundamental issue identified by the Judge as he commenced analysis of the experts giving evidence in this case was that those selected should reflect the averagely skilled man in the art or, as it may be, the skilled team. The role of the expert is to assist the court in the identification of the common general knowledge of the skilled man or team at the priority date. For the court to attach any weight to the evidence of the expert on these matters it would be most beneficial if the expert himself was typical of the skilled man in the art. Ideally, he should have knowledge of, and preferably experience in, the relevant field at the relevant date (he may thus have first-hand knowledge of some of the papers to which he is directed). In this particular case, Arnold J. concluded that the experts relied upon by MedImmune were not reflective of those in the skilled team and thus could offer limited assistance in relation to the common general knowledge in the field at the priority date. In contrast one Novartis expert was too skilled, leading the Judge to view his evidence in the context that he was acknowledged to be inventive, something which the hypothetical skilled man is not.

Arnold J. also raised concerns as to how one of the experts in the MedImmune case was instructed. Whilst in fact the expert was first provided with the relevant documents, asked for his views and only then allowed to see the patent in suit, his report was drafted in a way that did not reflect this, leading the judge to have some concerns as to the instruction process. Where experts have previously given evidence on the same matter in other jurisdictions there is of course the very real risk that any views expressed in the English case are tainted by hindsight, (especially if the UK instruction process as required was not followed).

And finally, the Judge was critical of the instruction of an expert whose first language was not English. Some readers may feel this is rather unfair, especially as in some cases this is very difficult to avoid. However in order to do right by the parties it is essential that the judge can understand all witnesses, and indeed make the most of their knowledge and experience. Of course Arnold J. was not advocating for only English experts to be instructed. Nevertheless we should be alive to the fact that any expert will be under pressure when giving evidence, and in order to do his best it is essential that he understands the questions completely and that what he says can be clearly understood.

This is not the first time these views have been expressed from the Bench. Experience shows however that lessons regularly need to be re-learned.