In O’Leary v Mercy University Hospital Cork Ltd [2019] IESC 48 the Supreme Court of Ireland made some telling observations on the role of the expert witness. Problems with experts are clearly not confined to one jurisdiction.


These opening comments show the universality of many of the issues relating to expert evidence at trial.

“Expert witnesses have played an important role in court proceedings since the earliest evolution of the common law. Such witnesses are often essential in assisting courts when reaching a conclusion on complex issues, whether they arise in a personal injury action, a commercial case, or a patent proceeding. However, there are, unfortunately, occasions when expert witnesses do not always appreciate their fundamental duty of independence and impartiality. Their primary duty is always owed to the court and not to their client or the person who retains them. The cost of obtaining expert testimony can form a significant component in overall litigation expenses. What may not always be clear, is that some cases where the ultimate outcome will be clear-cut actually come as far as the courtroom because of what are called “hired gun” witnesses on one side or the other. Quite often the deficiencies in the testimony of such witnesses are discovered only at the door of the court or in the hearing itself, by which time the parties may have incurred significant costs. This problem not only concerns private litigants and their advisers. At a time when litigation and insurance costs are a source of public concern, these problems can have a broader impact on the public. Prudent lawyers, acting in the interests of their clients, will always ensure that the expert testimony they seek to adduce will stand up to scrutiny in court. Sometimes, however, as in this case, there is a conflict of expert evidence. In this appeal, the appellant alleges that there was a conflict of interest in his High Court case derived from the level of the respondents’ witnesses’ remuneration, He says this created a perception of objective bias which should have rendered the respondents’ witnesses’ evidence inadmissible, or of little weight, thereby rendering the High Court action, in which he was plaintiff, unsatisfactory. As this judgment seeks to make clear there is a real distinction between the test for objective bias applicable to a judge or decision maker and on the other hand the duties of an expert witness to maintain independence and impartiality”


The plaintiff brought an action for clinical negligence. After a 21 day hearing his action was dismissed.  The bill of costs for defending the claim (which the plaintiff was liable to pay) came to €518,291.51. The defendant’s bill for expert witnesses came to €57,705.60 (later reduced to €48,000.)


The plaintiff’s main argument is summarised in the judgment.

“The appellant’s solicitors sought particulars of the claim for the expert witnesses’ fees. The claim was subsequently reduced somewhat to €48,000. The appellant alleges that, when analysed, the fees charged by two doctors who gave expert evidence for the respondents were so unusually high as to indicate a conflict of interest or what has been characterised in this appeal as ‘objective bias’, such as to call the entire High Court hearing into question and to render the trial of the action unsatisfactory.”

There was also a complaint that the defendant’s experts were provided with transcripts of the trial each day. This, it was argued, was to enable them to prepare their reports in an adversarial manner rather than simply report to the court.


The judgment set out the findings of the Court of Appeal
8. Speaking for a unanimous Court of Appeal, Peart J. dealt with the question of the remuneration of witnesses in some detail in his judgment. He set out the sequence of events leading to the appellant becoming aware of the medical witnesses’ charges. The judgment describes the evidence which was adduced by both sides in relation to the remuneration. This is described later in more detail. Peart J, adverted to the fact that a costs accountant engaged by the appellant to express a view on the medical fees, had stated on affidavit that their size was “unusual”, and that, in his extensive experience of taxing bills of costs, he had not come across fees of that scale before. Having outlined the appellant’s concerns, Peart J. went on to define the appellant’s case as being to the effect that the scale of the fees was such as to have “clouded the experts’ objectivity”, and that “without putting a tooth in it”, the allegation was that the witnesses’ support for the defendants’ case in the proceedings had been “bought”. The judgment made no criticism of the fact that the expert witnesses had been furnished with a transcript of the evidence on each day so as to keep up with the testimony. Counsel had criticised this on the basis that it was inappropriate for an independent and objective expert to “enter into the adversarial arena” and “advise” a party who instructed him or her as to their litigation strategy. Peart J rejected this submission, and also rejected counsel’s contention that this was a form of “prepping” an expert witness, thereby enabling them to tailor their evidence to meet the case made by the appellant during the hearing. Peart J. also outlined what was contained in affidavits sworn on behalf of the State Claims Agency defending the conduct of the two doctors. In fact, he observed that it was desirable that expert witnesses should know what is said on all sides.
9. Turning to the allegation of objective bias, Peart J. said that what was being contended for was in fact an accusation of unprofessional conduct; to the effect that the experts had given false or misleading evidence under oath, tailored to suit the case being made by the instructing principals. He was of the view that the issue was not suitable to be dealt with on appeal after the case had been concluded at first instance, bearing in mind that the doctors had no opportunity to address the matter on appeal. The appeal was dismissed on all counts.
10. By coincidence however, the issue of the fees charged in this case by the two doctors arose in another High Court action: Michael O ‘Driscoll (a minor suing by his next friend Breda O ‘Driscoll) v. Michael Hurley and the Health Service Executive (20th February, 2013; O’Neill J.), a case heard subsequent to the bill of costs being furnished. Counsel for the appellant also appeared as counsel for the plaintiff in O’Driscoll . During the course of that action, he cross-examined one of the same medical witness as to the fees he had intended to charge in that case. When the High Court judge asked counsel if he was suggesting that the fees being paid to Mr. Lanigan, one of the consultants, were a bribe and that the witnesses’ evidence had been bought, counsel declined to go that far, but submitted that where large sums of money were paid, witnesses were required “to go the extra mile”. As a matter of fairness, it is important to outline what Mr. Lanigan said in the O’Driscoll action in standing over his fee of €19,588 which he had charged in Mr O’Leary’s case, He described having to spend two hours each night over a period of three weeks reading transcripts sent to him by email. He said that he read these because he was asked to do so, and felt it necessary in order to defend his position against the plaintiffs’ expert witnesses, and such questioning as counsel may put to him. Mr. Lanigan testified that he spent three entire days attending the hearing of the High Court and that the fees charged were in line with what he had agreed in advance with the State Claims Agency. In the O’Driscoll case, Mr. Lanigan had agreed a fee of €5,000 per day for attendance at the High Court. The High Court judge hearing that case ruled that, so far as he was concerned, any further pursuit of the matter in cross-examination was a waste of time unless there was something else emerging from it. Counsel indicated he did not have evidence to tender the matter and would therefore move on. It emerged that in fact there was no agreement in relation to the witnesses’ fees prior to Mr. O’Leary’s case being heard in the High Court. In my view, such agreement is highly desirable and would avoid providing grounds for impugning a witness on the basis of conflict of interest.
11. The Court of Appeal (Ryan P, Irvine and Hogan JJ.) in O ‘Driscoll ([2015] IECA 158) rejected counsel’s submission that he should have been given a further opportunity to cross-examine Mr. Lanigan on the basis that he was not impartial, and that the fees were “egregiously extravagant” and “wildly above” anything the State Claims Agency could have been expected to pay. In effect, counsel’s case was that the doctor had become an advocate for the defendants, and that the fees at the level charged and agreed, were calculated to, or could introduce, a conflict of interest. His submission was that by agreeing to pay such fees, the Agency was inciting the witness to give partisan evidence. It is fair to say that there was a considerable lack of understatement in many of these criticisms.
12. Delivering judgment in the O’Driscoll appeal, Irvine J. criticised the possibility that an expert’s professional reputation might be treated as a disposable and worthless commodity and observed that such witnesses should not be allowed to become an open target for unrestricted questioning of a damning nature. She went on to hold that questions designed to tarnish the reputation of witnesses by reference to the level of fees charged should only be permitted where the party challenging the witness could state that it was their intention to call expert evidence to prove that the fees under scrutiny were exorbitant to the point that, in all the circumstances, the Court should consider that the validity or weight of the evidence to be in doubt.
13. The judgment in O’Driscoll has some bearing on the instant case, as in O’Driscoll , although making an allegation of objective bias and conflict of interest, counsel did not direct this Court’s attention to any specific part of the evidence which he claimed resulted from partiality or want of independence, or any specific issue where the want of either, as opposed to difference of opinion, might have arisen. Counsel based his case rather on the proposition that the nature and extent of the charges as allowed and paid in that case created the reasonable apprehension of conflict of interest, or what was characterised as objective bias. Whether objective bias could be the test for assessing conflict of interest for expert witnesses is addressed later in this judgment.



The Supreme Court looked at developments in other jurisdictions.

14. Issues concerning such witnesses are likely to become increasingly prevalent, not least as a result of the international nature of some types of litigation. While not cited, some recent case law in the neighbouring jurisdiction illustrates the breadth of the issues which can arise.
In the not entirely dissimilar case of Toth v. Jarman [2006] EWCA Civ 1028, the Court of Appeal of England and Wales (Potter P., Arden and Wall LJJ.) held that a court may conclude that a relationship between a party and an expert was so very close, to the extent that the expert’s evidence should not be admitted. Similar views are to be found in the English High Court judgment in Liverpool RC Trustees v. Goldberg (No.3) Ch. Div. 2001 WLR 2237.
15. The judgment of the Court of Appeal in EXP v. Dr. Charles Simon Barker [2017] EWCA Civ 63 illustrates that conflict of interests involving experts are not confined to the question of financial or economic interest in the outcome of a case. Irwin L.J.’ s judgment lucidly sets out the circumstances of a case where there had been an undisclosed close professional and social connection between the appellant, a doctor, and his principal expert witness, which neither party had declared. The judgment records that the trial judge concluded that, in fact, “steps had been taken” both in the curriculum vitae of the doctor and his expert witness which might have had the effect of avoiding the possibility of such connection might emerge. (paras. 23-28). The appeal judgment describes the appellant’s significant connections with the expert witness, an eminent neuro radiologist over many years, from training onwards. This had led the trial judge to seriously consider entirely excluding the expert witness’s evidence from the trial, although he decided not to adopt that course (para. 29). Nonetheless, what occurred significantly affected the weight which the judge was prepared to attach to his evidence (para. 32). Significantly, the judgment describes a number of specific medical issues where expert opinion was highly material to the outcome and where, in the case of a conflict, the question of weight to be given to such expert testimony would have been a strong consideration.



17. Against this background it is necessary to re-emphasise why the issue before the Court has some importance, and why the duties of expert witnesses require clear identification and definition. Other earlier case law acts a reminder of the distinction between a witness as to fact in contrast to an expert witness. The first is a witness who may not express an opinion with regard to the matters in issue between the parties. Rather, such a witness may testify only as to the existence of facts of which the witness has actual knowledge or experience. By contrast, an expert witness may express opinions in respect of such facts (see AG (Ruddy) v. Kenny [1960] 94 ILTR 185 at p.190 InRuddy , Kingsmill Moore J. explained the reasons for this distinction as including prejudice, faulty reasoning and inadequate knowledge. As experts, such witnesses enjoy a degree of latitude with regard to the general rules on admissibility of evidence for the purposes of assisting the court and finding and drawing inferences of fact in relation to matters which are not, and cannot be expected to be, within the experience of the fact finder, whether that be a judge or jury. The judgments in Ruddy identify the areas of expertise as being ones where there may be special study or experience required in order that a just opinion be formed, as in, for instance, “matters of art, science, medicine, engineering and so forth” (per Davitt P.). In Flynn v. Bus Atha Cliath [2012] IEHC 398, Charleton J. in the High Court drew attention to the fact that the entitlement of an expert to express an opinion was predicated upon informing the court of the factors which made up that opinion, and supplying the court with the elements of knowledge which study and experience had furnished, and which formed the basis of the opinion, so that, in the circumstances, the court may be enabled to take a different view to theirs (para. 9). As Charleton J. commented, experts are privileged by being able to express a view relevant to the issue before the court because of the unusual nature of their status and enables them to express a view; sometimes, but not in every case, on and matters relevant to those upon which the case may turn (para. 9). In short the role of such witnesses can be of great importance in assisting a court determine the outcome of any case; the more important the role the higher the duty of independence. Ultimately the judge, and the judge alone, must make the decision.”


Cases Where Remuneration is Not Guaranteed

21. In the English case of R ( Factortame Limited and Ors.) v. Secretary of State for Transport, Local Government and the Regions (No.8) [2003] QB 381, Lord Phillips M.R. addressed conflicts of interest, reiterating the oft-stated principle that it is desirable that an expert should have no actual or apparent interest in the outcome of proceedings in which he gives evidence, although pointing out that such interest was not automatically preconditional to the admissibility of such evidence. He pointed out that where an expert has an interest of one kind or another in the outcome of a case that fact should be made known to the court as soon as possible. I agree on both points.


26. In this appeal, reliance is placed on the case of the “Ikarian Reefer” ( National Justice Compania Naviera SA. v. Prudential Assurance Company Limited [1993] 2 Lloyd’s Rep 68). There, Cresswell J. in the English High Court identified the recognised principles and responsibilities of expert witnesses. As he pointed out the list is not exhaustive. As identified in that judgment, the principles are as follows:
(1) The evidence of such witnesses should be, and be seen to be , independent and uninfluenced in form or content by the exigencies of litigation;
(2) Such witnesses should provide independent assistance to the court by way of objective, unbiased, opinion in relation to matters within their expertise and should never act as advocates;
(3) Such witnesses should state the facts or assumptions upon which their opinion is based, and consider material facts which could detract from their concluded opinion;
(4) Expert witnesses should make it clear when a particular question or issue is outside their expertise;
(5) If such witnesses consider that insufficient data is available, they should say so, and indicate that the opinion is provisional only; and
(6) If the witness is not sure that their report contains the truth, the whole truth and nothing but the truth, without some qualification, they should state that qualification in their report. If an expert witness changes his views on a material matter such change of views should be communicated (through lawyers) should 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.
These duties have already been considered by our courts (see Payne v. Shovlin [2004] IEHC 430Donegal Investment Group Plc. v. Danbywiske and ors. [2016] IECA 193, at param 51.) I go no further than to point out that, in England and Wales, these rules have been further refined both in the case law ( Anglo Group Plc. v. Winther Browne & Co, Limited & BML (Office Computers) Ltd [2000] All ER (D) 294343) and elsewhere (see generally chapter 8 of the Law Reform Commission Report, cited at para. 6 above, which contains a full consideration of the law in many common law jurisdictions, including the England and Wales).


The Supreme Court rejected the claimant’s argument that the expert fees were so high as to give rise to a risk of bias.

32. Ultimately, counsel’s criticism comes down to two essential factual issues; first, the level and nature of the fees charged, and second, the question of the overnight transcripts. The fundamental questions are whether, even at their height, the materials put before the court were such as to render the trial unsatisfactory? Does the evidence demonstrate a potential that the witness is lacking independence to such a degree as would render the evidence which was admitted as being, in fact, inadmissible, or at least capable of being so significantly discounted in weight to the extent as to render the High Court trial unsatisfactory? Put more simply the questions are whether the witnesses should be regarded as so lacking independence so as not to have the characteristics of an expert witness; or more simply still, have the witnesses put their obligations to their client above their duty to the court? If the answer to these questions is in the affirmative, the consequence will foreseeably be that their evidence will attract little or no weight, and in serious cases may in fact be inadmissible. The evidence may be positively damaging to the case of the party who called the expert to give evidence.
33. It is true that there are unusual aspects to the fee arrangements in this case. It appears that the fees were not agreed or charged until after the case was completed. As indicated earlier, this is, I think, unusual and undesirable. Fee levels should be agreed beforehand. But in fact, it is hard to avoid the impression that the true objection to the fees charged is actually as to their size. I do not think that this can be seen as per se creating a conflict of interest or derogation from the duty of independence in the circumstances of this case. It is not hard to hypothesise a situation where, for examples an internationally recognised witness might submit a significant charge which is agreed to by a principal. This would not ipso facto render the evidence of such expert inadmissible.
34. The appellant has not established that there was any connection between the size of the fees and the nature of the testimony. By way of contrast to some of the English case law cited earlier, it has not been shown that there was some part of the evidence capable of being influenced, or potentially influenced, by partiality or conflict of interest. The fact that the respondent’ s witnesses testified against the appellant’s witnesses, even the fact that they may have expressed firm opinions, does not create a conflict of interest. The fact that such witnesses might have expressed a view in a statement of evidence does not indicate any breach of the duties outlined in the Ikarian Reefer either.


The Overnight Transcripts

43. I am unable to see that there could be any objection to the provision of overnight transcripts. It is by no means unknown for law cases to evolve during a hearing. Quite clearly, there were a number of different aspects to this 21-day case heard in the High Court. Altogether, the appellant called nine witnesses. It was not unreasonable for the respondents’ expert witnesses to be kept appraised of what these witnesses were saying and the manner in which the appellant’s case was developing as it proceeded, nor can I see any objection to the appellant’s expert witnesses attending court should they wish to do so. The fact that this may be a departure from previous practice some years ago does not indicate conflict of interest.

Contact with legal advisers

44. I also do not see an objection, per se , to the fact that, from time to time, counsel may wish to consult with an expert witness. But, correspondingly, such witnesses must be careful to ensure that they do not ever allow a situation to evolve where they put themselves, or are put in, the position of being seen as advocates rather than as independent witnesses.


  1. In England and Wales a case such as this would have been subject to cost- budgeting.  The expert fees (or at least those fees recoverable from the other party) would be known in advance, not fixed retrospectively.  (I am not wholly certain that a method of the experts meeting in advance and agreeing the issues between them exists in this jurisdiction).
  2. Tens of thousands of Euros were spent on expert witnesses, however it is ironic that the case rested, ultimately, on lay witness credibility.                                                                                                                         ” in fact, the consent issue turned on a question of credibility. Quirke J. concluded that the appellant was not a reliable witness as to what had taken place in his meetings with Mr. Al-Safi. He observed that Mr O’Leary’s sister, who the appellant said in court was an eye-witness, had not given corroborative evidence in support of his case that he had not been adequately informed of the risks of the procedure”