The Role of an Expert Witness

In some civil court and tribunal cases a report from an "expert" such as a medical consultant, engineer, it-consultant or surveyor, is needed.

For example, in the case of an unstable wall, a surveyor or structural engineer may be asked to write a report giving an assessment of the present condition of the wall, what remedial work is needed, and how much the remedial work is likely to cost. In doing this the expert is examining something (the wall) which presently exists and giving an opinion. Sometimes, however, an expert is asked to give an opinion on partly assumed facts. For example the question put to the expert might be "assuming that the damage to the wall was caused by impact by a Land Rover Defender 90, at what speed would the Land Rover have been travelling at the time of impact?" The reason why an expert may be asked such a question is that the expert's evidence is only part of the evidence which will be considered by the court or tribunal - there may be the evidence of eyewitnesses who can describe the vehicle involved. Different witnesses may have differing recollections and the expert's opinion on assumed facts, together with the other evidence in the case, assists the judge to reach a finding on what actually happened.

Sometimes an expert is asked to give an opinion on assumed facts but is, in addition asked whether, by reason of their expertise, the expert can give a view on the likelihood of the assumed facts being true. An expert must only give opinions which they are competent to give within the area of their own discipline and a good expert will stick faithfully to this limitation. An expert might be tempted to comment on the likelihood of the accident having happened in the way one of the parties claims but the expert can only properly do so if their expertise gives them a particular insight not simply because ordinary human experience makes them think the claim likely or unlikely. The expert must not confuse their role with that of the judge.

An expert therefore needs to understand the role of an expert in a legal case as well as being trained in a particular discipline.


The above explanation of procedure is only an overview and in order to be reasonably concise I have had to leave some details out - details which are likely to affect what the procedural rules would say about your own situation. So please do not rely on the above but contact me for advice

This page was lasted updated in August 2018 Disclaimer