Ethics and the role of the expert witness

The ethical obligations of a witness called upon to give expert opinion evidence are more complex than just telling ‘the truth, the whole truth and nothing but the truth’. An expert witness - and particularly a forensic scientist - is relied upon by the court to examine certain evidence and draw inferences from it that the court could not draw for itself. The Forensic Science Regulator Code of Conduct for Forensic Practitioners enjoins scientists to ‘provide expert advice and evidence only within the limits of professional competence’. Experts may trespass on the expertise of other professions or - a matter of equal if not greater concern to the courts - they may stray into areas that the law does not consider to be matters of expert opinion at all. A particularly delicate situation arises where an expert is confronted with an opposing opinion from another expert who has more specialised knowledge on the relevant aspect of the case.