As those of you who undertake expert witness work will know, an expert's duty, as formulated by Mr Justice Cresswell in the Ikarian Reefer* case, is to 'provide independent assistance to the court by way of objective unbiased opinion in relation to matters within his expertise'.
The expert's primary duty is to the court. But must the expert necessarily be independent of the party on whose behalf they give evidence?
The question can be particularly pertinent in specialised technical disputes where expertise in a particular field is limited and experts and parties are well known to each other.
In the recent case of the Liverpool Roman Catholic Archdiocesan Trustees v Goldberg [2 March 2001], the claimants sued a QC who had advised them on tax matters, upon which advice the claimants relied. Unhappily, the Inland Revenue took another view and the claimants had to pay some tax that might otherwise have been avoided.
In his defence, Mr Goldberg sought to rely on the expert evidence of Mr Flesch QC, another tax specialist. The two men had known each other for 28 years and were good friends.Mr Flesch properly acknowledged this at the beginning of his report. The claimants tried to exclude Mr Flesch's evidence, saying he could not be independent, and independence was an essential ingredient of expert evidence. Mr Justice Neuberger disagreed with the claimants, and the fact that defendant and expert were friends did not necessarily mean that Mr Flesch was unable to fulfil the role of an expert.
In December 1999 the Court of Appeal considered a similar question in Field v Leeds City Council , in which the claimants complained about the lack of repairs carried out by their local authority landlord. Leeds wanted to rely on the expert evidence of Mr Broadbent, an employee in their housing services claims-investigation section. The Court of Appeal decided that the only questions that governed whether Mr Broadbent should be able to give expert evidence were, first, whether he had relevant expertise in relation to the issues, and second, whether he was aware of his primary duty to assist the court. Hence Mr Broadbent's evidence was not excluded simply because he was an employee of the defendant.
But this does not mean that it is necessarily a good idea to call upon the expert evidence of your best friend or employee. The court may listen to the evidence, but it is open to the judge to decide what weight it has.
Lord Woolf said there could be obvious advantages for the court to be presented with an expert not employed in Mr Broadbent's role.
In the Liverpool case Mr Justice Neuberger commented that the friendship of Mr Goldberg and Mr Flesch might provide fertile grounds for cross-examination by the claimants, and it would be open to the trial judge to discount entirely Mr Flesch's evidence or to treat it with considerable care. Had Mr Flesch not openly acknowledged his friendship in his report and the claimants found it out, their crossexamination could potentially be still more damaging to Mr Flesch's credibility as a witness.
Assessing the weight to be given to each piece of evidence is something judges are well practised at. They spend much of their time listening to competing evidence and deciding which witness's testimony to prefer.
At the end of the day, in Mr Justice Neuberger's words, 'any judge worth his salt should be able to assess whether Mr Flesch is independent'.
So it is open to a party to adduce the expert evidence of someone well known to them.That a witness may not be independent from their party should not be confused with a lack of independence of opinion.
However, where there are other experts available it might be prudent to consider instructing them instead. Similarly, anyone approached to give expert evidence should make plain any association with the parties, allowing those instructing them to take into account the risk that the court might accord different weight to their evidence.
*The full name of the case is National Justice Compania Naviera SA v Prudential Insurance Co [although it is much better known as the Ikarian Reefer, the name of the ship involved], reference  2 Lloyd's Rep.68 at 81.