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[This article was originally published in Law Ireland in March 2019]
It may normally be assumed that a professional will aim to comply with the duties of his or her profession. Standards are set down in almost every field, and it is reasonable to suppose that most members of the relevant profession as a rule will abide by them.
It seems that no such assumption can be made in relation to professionals who step outside their day-to-day duties and act as expert witnesses. Their duty is clear; it is to assist the court in reaching a decision, and not to act as a ‘hired gun’ for the parties who retain them.
This duty is so well established that it hardly needs to be re-stated, and is discussed at some length in the Law Reform Commission’s 2017 Report on Consolidation and Reform of Aspects of the Law of Evidence, at 8.17 et seq. It has now been set out clearly and succinctly in Order 39, rule 57 of the Rules of the Superior Courts (as inserted by SI 254 of 2016):
“57. (1) It is the duty of an expert to assist the Court as to matters within his or her field of expertise. This duty overrides any obligation to any party paying the fee of the expert.”
Case law would suggest that this is more honoured in the breach than the observance. In Byrne v. Ardenheath  IECA 293 (Court of Appeal, Irvine J, 9 November 2017), Ms Justice Irvine made the following observation:
"It was my experience as a trial judge that the effectiveness of the assistance offered by expert witnesses in almost all disciplines, whether that evidence was in respect of the standard of care proposed or a party's compliance therewith, was frequently compromised by the fact that, all too often, their opinions all too often appeared to correspond too favourably with the interests of the parties who retained them. I continue to remain of that view as an appellate court judge where the transcript may lead one to the conclusion that a given expert had become so engrossed in their client's position that they were clearly incapable of providing truly independent guidance for trial judge.”
These comments have been quoted with approval in several judgments in the fourteen months since they were delivered. But many other cases have suggested that experts are excessively swayed by sympathy for their own side, and do not have sufficient regard for the duty towards the decision maker.
In Hanrahan v. Minister for Agriculture  IESC 66 (Supreme Court, O’Donnell J, 18 October 2017), experts on either side were tasked with valuing 223 cattle that had been wrongfully sold by the defendant. One expert assessed the loss at over €800,000. The other expert assessed it at €1,979. Mr Justice O’Donnell commented:
“I do not wish to criticise the individuals who gave evidence in this case, since this was a difficult case and in any event the “high ball – low ball” approach which occurred here is only an example of a more widespread phenomenon. However, it is surely not coincidental that it was the independent expert on behalf of the plaintiff whose opinion was that the damages were extremely substantial, and the expert on behalf of the defendant who considered that in effect there was no loss at all.”
With the recent introduction of special rules on expert evidence, including provision for single joint experts, questions to experts, joint inspections, joint reports and a ‘debate among experts’, it is likely that the position of experts will be under greater scrutiny.
Expert witnesses should also be aware that their perceived immunity from suit has been set aside in the UK, in the case of Jones v. Kaney  UKSC 13 (Supreme Court, 29 March 2011). The decision is hard to argue with, and it seems likely that the Irish courts would follow suit if an appropriate case arose.