Expert Witnesses must always be aware that their primary job is to assist the Court and not to be an Advocate for the party that has retained them. For a Court to be able to rely on the evidence of an Expert Witness the following guidelines will be of assistance:
- An Expert Witness should at all stages provide independent assistance to the Court.
- The Expert Witness should not give evidence as to what the expert would have done in similar circumstances or otherwise seek to usurp the role of the judge.
- An Expert Witness should co-operate with the expert of the other party.
- The expert evidence presented to the Court should be, and should be seen to be, independent.
- An Expert Witness should state the facts and/or assumptions upon which their opinion is based.
- An Expert Witness should make it clear when a question falls outside their experience.
- An Expert Witness must say explicitly if they think their conclusions are based on inadequate facts.
- An Expert Witness must be ready to reconsider their opinion.
Point 2 presents an easy trap to fall into in relation to assessing the conduct of a professional. The real question to be addressed by the expert is whether the professional acted in accordance with a practice accepted at the time as proper by a responsible body of opinion skilled in the relevant field (Bolam v Friem Hospital Management Committee (1957) 1 WLR 582).