Expert Witnesses: playing by the rules

Expert witnesses are under increasing pressure in both civil and criminal proceedings. They must comply with the Civil Procedure Rules and relevant guidelines. Experts who fail in their duties are sometimes singled out for fierce criticism by judges, as a recent criminal case illustrates.

Instructing solicitors need to exercise caution when choosing an appropriate expert witness, to protect themselves and their client.

Obligations to the court
An expert witness’s primary obligation is to the court, a duty overriding their duties to the parties and their solicitors. Their evidence must be independent and objective, and unbiased towards the paying party. Their written and oral evidence must be truthful and provide an honest opinion of the issues, and they must, of course, be suitably qualified and experienced.

The ruling in Pabon, R v [2018] EWCA Crim 420 is important in the context of expert witnesses and instructing solicitors for highlighting the problems that can arise if an expert is not sufficiently experienced. The appeal concerned the conduct of an expert witness in a LIBBOR-fixing trial who “fared disastrously”. As the court highlighted, he lacked experience for the task in hand (in fact, the defendants in the trial sought a pre-trial hearing to exclude or restrict his evidence on the ground of lack of expertise).

The expert had general banking experience but had never worked as an interest rate derivatives trader, a cash desk trader or a LIBOR submitter, and appeared to have no direct knowledge of the LIBOR submission process. Nor, as noted by the Court, had he worked as a trader of any kind since 2000 and, from 2005 onwards, he had acted as a professional expert witness on general banking disputes. He was, in Bingham LJ's words, no more than an "enthusiastic amateur”.

The Court of Appeal reiterated: “…to state the obvious, expert evidence must be expert; it can only be such if it is within the expert's area/s of expertise; if the so-called expert witness gives evidence outside of his area/s of expertise it is both of no use to the jury and corrosive of the trust placed in such witnesses.” The Court also said that however the expertise is acquired, “the expert must be confined to matters within his area/s of expertise”.

The expert employed here had “signally failed to comply with his basic duties as an expert.” He had, for instance, not told the SFO or the court of the limits to his expertise, and in his evidence he strayed into areas beyond his expertise. Even his actual conduct was severely criticised: he had signed declarations of truth and of understanding his disclosure duties. However, he did so recklessly, or knowing that he had failed to comply with these obligations.

The ruling is an important reminder for solicitors to ensure they are satisfied as to the witness' expertise and to ensure they are of suitable calibre.



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