The expert witness’s duty

A somewhat skewed take on the expert’s duty was displayed by the expert in Pepe’s Piri Piri Ltd v Junaid [2019] EWHC 2097 (QB).  He recognised that his ultimate duty was to the court but also asserted that where he was instructed by a particular party then he would do the best that he could to present that party’s case in the most favourable light.  As the judge observed, that approach was not consistent with the duties of an expert under Part 35 of the CPR.  It is no part of an expert’s role when instructed in litigation ‘to present the party’s case in the most favourable light’.  The expert must present evidence as in independent expert and uninfluenced by the pressures of litigation.  His evidence should be the same whichever side he is instructed on behalf of.

The expert had slipped into the role of an advocate for the party instructing him.  He provided a critique of the other side’s action and in doing so introduced matters outside his area of expertise.

The consequence was that little weight could be put on the expert’s evidence at any point where he was in conflict with the other side’s expert, who had not erred in this manner.

It is extraordinary that expert witnesses should still fall into these errors.  A basic reading of the Rules, Practice Directions and the Guidance for the Instruction of Experts in Civil Claims, let alone any training they may have received, would leave no room for confusion.  Medical experts can gain a little comfort from the fact that this was an accounting expert being criticised on this occasion!

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