What is the position where a litigant instructs an expert to comment upon matters within their expertise and the expert, whilst producing an acceptable overall report, trespasses into areas which are the realm of the trial judge? Should the opposing party be allowed to strike-through and redact the offending passages so as to ensure that the judicial mind remains free and unpolluted by irrelevant material? Is this really a proportionate response to the problem, particularly in an era in which the Courts have been at pains to emphasise the importance of avoiding unnecesary and costly satellite litigation?

This was one of many issues which arose in the recent decision of the High Court in Hoyle v Rogers (2014) EWCA Civ 537, a case concerned with the admissibility at trial of an air-accident investigation report into a fatal aircraft crash. Christopher Clarke LJ expressed the view that there was nothing to be gained, except in 'very clear cases', from excluding or excising sections of expert reports in advance of trial. He specifically approved the comments of the first instance judge, which are worth repeating in full:

"Such an exercise is unnecessary and disproportionate especially when such statements are intertwined with others which reflect genuine expertise and there is no clear dividing line between them. In such circumstances, the proper course is for the whole document to be before the court and for the judge at trial to take account of the report only to the extent that it reflects expertise and to disregard it in so far as it does not. As Thomas LJ trenchantly observed in Secretary of State for Business Enterprise and Regulatory Reform v Aaron [2008] EWCA Civ 1146 at para 39:

 "It is my experience that many experts report views on matters on which it is for the court to make its decision and not for an expert to express a view. No modern or sensible management of a case requires putting the parties to the expense of excision; a judge simply ignores that which is inadmissible."

In this author's experience, this clear judicial warning is very often ignored in practice. It is not at unusual for parties to find themselves embroiled in internicine interlocutory applications about one or two paragraphs scattered throughout expert reports which are otherwise unobjectionable. It will be instructive to see whether the Court of Appeal's restatement of the correct approach begins to turn the tide.