Expert Witness: a cautionary tale

  • Published: May 23, 2018
  • Author: Paul Sankey, Partner, Enable Law

An expert witness is criticised by the Court of Appeal

The Court of Appeal judgment in R v Pabon is a cautionary tale for experts. In this case, the Court of Appeal was highly critical of an expert's conduct in a criminal trial [1].

Medical experts might look at this case and think that the lessons do not apply to them. The case involved a banking expert who flouted the Criminal Procedure Rules. However, an expert's duty is much the same whether giving evidence in civil or criminal cases. There are lessons to be learnt for all experts.

The Serious Fraud Office (SFO) prosecuted several employees of Barclays Bank PLC. One of them was Mr Pabon. He was found guilty of conspiracy to defraud. The conspiracy involved dishonestly rigging the LIBOR (London Inter-Bank Offered Rate – the interest rate at which banks borrow money from each other).

The SFO called Mr Rowe as an expert witness. He had given evidence on two occasions in earlier LIBOR trials. He gave evidence about banking terms and concepts, and various matters concerned with banking practice. This was not a subject about which he was an expert.

Mr Pabon was convicted after a retrial. Mr Rowe had been called to give evidence, both at the first trial and at the retrial. Some 'dramatic developments' occurred in relation to his evidence during the retrial.

1.    The defence produced emails which demonstrated that some of his report had, in fact, been prepared by Mr O'Kane. Mr O'Kane was a partner at Mr Rowe's firm. He was also a part-time Professor of Pricing and Risk Financial Derivatives. Mr Rowe had not indicated that he had relied on anyone else in giving evidence.

2.   Further, Mr Rowe had sent extracts from the case papers to other specialists. He had sought their guidance on some issues. In the month before giving evidence, he exchanged about 60 text messages with one and 27 with another. There were also exchanges of numerous emails with them and with a third expert.

When Mr Rowe finished giving evidence on the first day of the retrial, the judge gave him a (standard) warning not to discuss his evidence with anyone. Within an hour, he had approached someone for assistance, asking for 30 minutes of paid work. In his message he commented, "I don't know the usual trades STIR people put on but I am learning". He later added, "It doesn't help when I have to explain a few emails and look knowledgeable". He exchanged a total of 26 texts or emails.

3.    In cross-examination, he was asked whether he had read the Criminal Procedure Rules when he signed his report. His response was, "I don't think I could have read them fully". Answering a supplementary question, he said, "I'm pretty sure I glanced at something". When he was confronted with the fact that he had approached others to explain what he did not understand, his answer was, "So what else am I supposed to do as an expert?" As the defendant's counsel pointed out, the correct answer was, '" Say it is not my field; I cannot give you expert opinion; you the SFO should go and speak to someone else".

4.    He said in Court that he had spoken to the SFO and indicated that he was not a STIR expert. This contradicted what the SFO's principal investigator had said.

When summing up, the judge's comments to the jury included:

"…you may have formed a judgment that he knew very little about the duties of an expert…he seems to have been perfectly content to sign a standard declaration in which he declared that he had read the Criminal Procedure Rules which govern his conduct as an expert, both before trial and in giving evidence, and the booklet on his duties of disclosure without doing anything really to familiarise himself with either of these documents".

Mr Pabon's appeal against his conviction was heard by the Court of Appeal in November 2017. The judgment was published in March 2018.

Central to the appeal was Mr Rowe's evidence. On the facts, the appeal failed. The shortcomings in his evidence did not make the conviction unsafe. However, the Court of Appeal was highly critical of Mr Rowe. In the words of Lord Justice Gross, the evidence of experts outside their area of expertise is not just "of no use". It is "corrosive of the trust placed in such witnesses". He set out his criticisms of the expert:

"Put bluntly, Rowe signally failed to comply with his basic duties as an expert…he signed declarations of truth and of understanding his disclosure duties knowing that he had failed to comply with those obligations alternatively, at best recklessly. He obscured the role Mr O'Kane had played in preparing his report…he did not inform the SFO, or the Court, of the limits of his expertise. He strayed into areas in his evidence (in particular STIR trading) when it was beyond his expertise (or, charitably, at the outer edge of his expertise)…In this regards he was not more than…an 'enthusiastic amateur'. He flouted the judge's admonition not to discuss his evidence whilst in the witness box. We take a grave view of Rowe's conduct; questions of sanction are not for us, so we say no more of sanction but highlight his failings for the consideration of others."

The judgment ends with a final comment:

"…there is no room for complacency and this case stands as a stark reminder of the need for those instructing expert witnesses to satisfy themselves as to the witness's expertise and to engage (difficult though it sometimes may be) an expert of a suitable calibre."

The moral of the story is: understand your duties as an expert, comply with them, and only give evidence on matters within your area of expertise.


[1] R v Pabon [2018] EWCA Crim 420. I am grateful to Gordon Exall's Civil Litigation Brief for highlighting this case.



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