Mr Justice Cresswell set out the following rules for experts in National Justice Compania Naviera SA v Prudential Assurance Co Ltd (The Ikarian Reefer) [1993] 2 Lloyd's Rep. 68 at 81-82: 

1. Expert evidence presented to the court should be, and should be seen to be, the independent product of the expert uninfluenced as to the form or content by the exigencies of litigation (Whitehouse v Jordan [1981] 1 W.L.R. 246, HL, at 256, per Lord Wilberforce). 

2. An expert witness should provide independent assistance to the court by way of objective unbiased opinion in relation to matters within their expertise (see Pollivitte Ltd v Commercial Union Assurance Company Plc [1987] 1 Lloyd's Rep. 379 at 386, per Garland J., and Re J (1990) F.C.R. 193 , per Cazalet J. An expert witness in the High Court should never assume the role of an advocate. 

3. An expert witness should state the facts or assumption on which their opinion is based. They should not omit to consider material facts which could detract from their concluded opinion (Re J, above). 

4. An expert witness should make it clear when a particular question or issue falls outside their expertise. 

5. If an expert's opinion is not properly researched because they consider that insufficient data are available then this must be stated with an indication that the opinion is no more than a provisional one (Re J, above). In cases where an expert witness who has prepared a report could not assert that the report contained the truth, the whole truth and nothing but the truth without some qualification that qualification should be stated in the report (Derby & Co Ltd v Weldon (No.9), The Times, November 9, 1990, CA, per Staughton L.J. 

6. If, after exchange of reports, an expert witness changes their view on the material having read the other side's expert report or for any other reason, such change of view should be communicated (through legal representative) to the other side without delay and when appropriate to the court. 

7. Where expert evidence refers to photographs, plans, calculations, analyses, measurements survey reports or other similar documents, these must be provided to the opposite party at the same time as the exchange of reports