1. Expert evidence presented to the court should be, and should be seen to be, the independent product of the expert uninfluenced as to form or content by the exigencies of litigation
2. An expert witness should provide independent assistance to the court by way of objective unbiased opinion in relation to matters within his expertise.
3. An expert witness should state the facts or assumptions upon which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion.
4. An expert witness should make it clear when a particular question or issue falls outside his expertise.
5. If an expert's opinion is not properly researched because he considers that insufficient data is available, then this must be stated with an indication that the opinion is no more than a provisional one.
6. If the expert cannot assert that the report contains the truth, the whole truth and nothing but the truth without some qualification, that qualification should be stated in the report.
7. If, after exchange of reports, an expert witness changes his view on a material matter having read the other side's expert's report, or for any other reason, such change of view should be communicated (though legal representatives) to the other side without delay and (where appropriate) to the court.
8. Where expert evidence refers to photographs, plans, calculations, analyses, measurements, survey reports, or other similar documents, they must be provided to the opposite party at the same time as the exchange of reports.
A more recent case further clarified the role of the expert witness (Toulmin HHJ in Anglo Group plc v Winther Brown & Co. Ltd.2000)
1. An expert witness should at all stages in the procedure, on the basis of the evidence as he understands it, provide independent assistance to the court and the parties by way of objective unbiased opinion in relation to matters within his expertise. This applies as much to the initial meetings of experts as to evidence at trial. An expert witness should never assume the role of an advocate .
2. The expert's evidence should normally be confined to technical matters on which the court will be assisted by receiving an explanation, or to evidence of common professional practice. The expert witness should not give evidence or opinions as to what the expert himself would have done in similar circumstances or otherwise seek to usurp the role of the judge.
3. He should co-operate with the expert of the other party or parties in attempting to narrow the technical issues in dispute at the earliest possible stage of the procedure and to eliminate or place in context any peripheral issues. He should co-operate with the other expert(s) in attending without prejudice meetings as necessary and in seeking to find areas of agreement and to define precisely areasof disagreement to be set out in the joint statement of experts ordered by the court.
4. The expert evidence presented to the court should be, and be seen to be, the independent product of the expert uninfluenced as to form or content by the exigencies of the litigation.
5. An expert witness should state the facts or assumptions upon which his opinion is based. He should not omit to consider material facts which could detract from his concluded opinion.
6. An expert witness should make it clear when a particular question or issue falls outside his expertise.
7. Where an expert is of the opinion that his conclusions are based on inadequate factual information he should say so explicitly.
8. An expert should be ready to reconsider his opinion, and if appropriate, to change his mind when he has received new information or has considered the opinion of the other expert . He should do so at the earliest opportunity.