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Inexpert Experts


A recent UK trial involving a multi-million-pound carbon credit fraud against eight defendants collapsed after an expert witness was found to be inadequately qualified upon cross-examination by defence counsel. It is a useful reminder of the risk of instructing an inexpert expert.  The collapse of this criminal trial could potentially result in over 20 additional fraud trials being declared unsafe.

The expert was engaged by the prosecution to act as an expert witness in the trial of eight men accused of committing a carbon credit fraud. His lack of academic qualification, the fact that he had never read a book on carbon credits, his inadequate storage of sensitive documents which were damaged by a leak and the fact that he had cut and pasted witness statements from previous trials became clear during his cross-examination.  

The trial judge stated that the expert: “…  is not an expert of suitable calibre. He had little or no understanding of the duties of an expert. He had received no training and attended no courses. He has no academic qualifications. His work has never been peer-reviewed”.

Position in Ireland

An expert witness’ role is to assist the court in making its decision and not to act as a hired gun. The Irish courts have addressed the issue on multiple occasions, most recently by the Supreme Court in O’Leary v Mercy University Hospital Cork Ltd IESC 48 where Mr. Justice MacMenamin referenced expert witnesses’ duties, including the duty to only address areas within the expert’s expertise.  Whilst the expert in those proceedings was judged to have acted independently, objectively and in an unbiased fashion, MacMenamin J. did comment that the duties of expert witnesses should be further outlined in Practice Directions, which indicates some concern about the current specificity of expert standards. The Law Reform Commission have also made recommendations about the duties of expert witnesses which we previously considered here.

The Supreme Court considered the principles for experts as set out in ‘Ikarian Reefer’1, a 1993 UK case, which has previously been cited in Ireland. One factor (amongst others) is that an expert should make it clear when a particular question or issue is outside their expertise – therefore, if the entire issue is outside their expertise, they should refuse all instructions. 

Expert Witness Immunity

This begs the question as to what happens if an expert witness proceeds to address a question or issue outside their expertise.  In the UK expert witnesses’ automatic immunity has been dispensed with, which we previously discussed here.  In Ireland, expert witness immunity still applies.  However, there is a growing consensus that this may change and the Law Reform Commission report2 supports that consensus.  The report also suggested that the existing expert immunity should be abolished and replaced with a statutory provision that an expert can be sued if it is established that they acted with ‘gross negligence‘ when giving their evidence or in preparing their expert report. Generally, “gross negligence” means falling far short of the standard expected or a very high degree of negligence but this will be dependent on the circumstances in each case. Indeed, the UK Supreme Court has stressed that in practice, liability of experts ought to be “highly exceptional”.

Key Considerations

The Irish courts will render negative findings in respect of purported expert evidence where the expert is clearly inexpert.  In addition, whilst immunity prevails, the judiciary have shown an inclination to take corrective actions where an expert acts contrary to requirements.  Those actions include notifying the purported expert’s regulatory authority of negative findings against an expert’s evidence.  Experts, instructing solicitors and, most importantly, inexpert(s) should bear this in mind.

For further information, please contact any member of the William Fry Litigation & Dispute Resolution team or your usual William Fry contact.


1 National Justice Compania Naviera SA. v. Prudential Assurance Company Limited 2 Lloyd’s Rep 68

2 LRC 117-2017, ‘Consolidation and Reform of Aspects of the Law of Evidence’.





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