Brilliant though it is the Secret Barrister’s book has not tempted me to write about criminal law. However it is always worthwhile keeping a weather eye on the behaviour and conduct of experts.   Problems with experts are very similar across all jurisdictions.   The case of Pabon, R v [2018] EWCA Crim 420 is an illuminating one. A decision of the Court of Appeal Criminal Division  – it could well form part of a chapter when SB writes the second edition.

“Put bluntly, Rowe signally failed to comply with his basic duties as an expert. As will already be apparent, he signed declarations of truth and of understanding his disclosure duties, knowing that he had failed to comply with these obligations alternatively, at best, recklessly.”


The appellants were arguing that a conviction was unsafe.  He had been convicted at a trial of manipulating the LIBOR rate.  A retrial took place in relation to some of his co-defendants, they were acquitted. At both trials the prosecution relied on the evidence of an expert, Mr Rowe.  However at the retrial of the co-defendants it became clear that this evidence was far from perfect.


The rules governing the instruction and conduct of experts in criminal proceedings are, to all intents and purposes, identical to the duties owed in civil procedure. The expert was instructed accordingly.

 Mr Rowe was instructed by the SFO (“the letter of instructions”) to provide an expert report “explaining the workings of an investment bank, inter-dealing brokerage and related financial instruments and trading terms used by individuals within these institutions”. As background, Rowe was informed that the SFO was investigating allegations that “between 2005 and 2010, LIBOR was dishonestly manipulated across a number of different currencies and tenors”. The instructions were thus generic, to the forthcoming series of anticipated LIBOR trials. Included amongst the areas Rowe was instructed to cover were an overview of the trading floor and an explanation of the different types of traders within an investment bank and their functions. The letter of instructions drew specific attention to the duty of an expert “to give objective unbiased opinion on matters within their expertise”, together with the relevant provisions of the Crim PR.


    1. The retrial: The retrial saw dramatic developments concerning Rowe’s evidence. The matter is most helpfully introduced through the witness statement of Mr Kuhn, dated 24th May, 2017 (forming part of the fresh material), a legal representative acting on behalf of Reich at the retrial.
    2. At the retrial, Rowe began his evidence on 9th March 2017. Pressed on the 9th and 10th March for disclosure by the defence, Rowe provided e-mail correspondence revealing that Mr Dominic O’Kane, a partner at Rowe’s firm and a part-time Professor of Pricing and Risk Financial Derivatives, had been responsible for drafting sections of Rowe’s report. This was not previously known.
    3. Furthermore, as Mr Kuhn recorded, the newly disclosed material revealed:
“5. ….that prior to April 2016 Mr Rowe had sent excerpts of the case papers to Ms Signe Biddle an interest rate derivatives trader and financial consultant at RBS and Mr Michael Zapties, Head of Rates Trading at HSBC and sought their assistance.
6. On Friday 10 March 2017 I contacted both Ms Biddle and Mr Zapties. I spoke with each by phone on 15 March 2017. They both said that they had been contacted by Mr Rowe and that in the course of their respective conversations he had neither told them that he was acting as an expert witness in a criminal trial, nor had he explained to them the caution which they should exercise in expressing an opinion.
7. On the weekend of the 11 March 2017 Mr Rowe provided further material to the SFO, in the form of text messages between Mr Rowe, Ms Biddle and Mr Zapties…..
8. From the additional disclosure it appeared that in the month prior to his giving evidence in the 2016 trial, Mr Rowe exchanged around 60 text messages with Ms Biddle and 27 text messages with Mr Zapties, as well as numerous emails with both them and Mr Nick Van Overstraeten, a third expert.”
    1. It may be noted that these exchanges included reference to STIR trading, a technical area which Rowe purported to cover when giving evidence.
    2. So far as concerns the exchanges between Rowe, Ms Biddle, Mr Zapties and Mr Van Overstraeten, matters do not end there. A remarkable feature of the newly disclosed material was the revelation that at the conclusion of the first day of his evidence at the trial – and having been expressly warned by the Judge not to discuss his evidence until it was concluded (see above) – Rowe went on to do just that.
    3. Within an hour, he sent a text to Ms Biddle, asking her to do “30 minutes (paid!) work tonight”, explaining that he needed an “interpretation of a STIR/OIS [Overnight Index Swap] email”. In the course of further exchanges with Ms Biddle, Rowe said “I don’t know the usual trades STIR people put on but I am learning”. Ms Biddle emphasised the importance of context, to which Mr Rowe agreed but added “…it doesn’t help when I have to explain a few emails and look knowledgeable”. On the same night, he remarked to Mr O’ Kane that he would do no more STIR cases; they would engage a STIR specialist, “as the mission has crept beyond where it was meant to for me”. In cross-examination at the retrial, he explained this by saying that he was “at the edge” of his expertise.
    4. Overall, between the conclusion of his evidence on the 13th April 2016 and resuming his evidence on the 14th April, Rowe exchanged some 26 texts or e-mails with Ms Biddle and Mr Zapties. When questioned on the 14th April, he made no mention of his contacts with Ms Biddle, Mr Zapties and Mr Van Overstraeten, notwithstanding, put at its lowest, their important contribution to the answers he gave.
    5. Inevitably, Rowe was subjected to damaging cross-examination (by Mr Darbishire QC) at the retrial on this rich seam of material, including his duties as an expert and the declaration in his report, required by the Crim PR. His answers were such as to prompt the following exchange with the Judge:
” Q: Are you really saying that when you signed off the declaration which I suspect is in standard form, you hadn’t in fact read either the CPR or the booklet?
A: I don’t think I could have read them fully….
Q: Did you read them at all?
A: I’m pretty sure that I glanced at something.”
    1. There was, likewise, equally damaging cross-examination as to Rowe’s expertise, including this passage:
” Q: What you did in 2016 was to start pinging out emails and texts to people, passing on the material you had been provided with by the SFO and saying to people: can you help me to understand it because I don’t understand it? That’s what you did isn’t it?
A: So what else am I supposed to do as an expert?
Q: Say it is not my field; I cannot give you an expert opinion; you the SFO should go and speak to someone else.
A: I think I have had conversations with the SFO to check that they know that I am not a STIR expert. “
The difficulty with this last answer (and others similar to it) was that the SFO’s principal investigator, Mr McLaughlin, gave evidence at the retrial saying that he had not been present at any discussion with Rowe in which Rowe had told the SFO that he was not qualified to express an opinion on any issue in the case.
    1. The Judge’s summing-up at the retrial was telling as to Rowe’s evidence, in an extended passage early in his summing-up:
“Despite that catalogue of experience, you may have formed a judgment that he knew very little about the duties of being 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 those documents.
It will be for you to judge whether he has in fact given expert opinion which falls outside his true expertise.
Any expert is entitled to research a topic on which he is to give evidence and obtain the views of others, including work colleagues, about it to enhance his opinion, so long as he records where he went for that advice and so long as it is to enhance an expertise he already has, rather than to become an expert on a subject where he has no knowledge whatsoever.
There seems to be no dispute that he has a general expertise in banking and finance and that many of the issues he dealt with involved basic matters which are not in dispute.
……But there are other areas of his evidence where you would be entitled to conclude that he has gone beyond his general knowledge of banking into very specific areas, which were at the very edge of or beyond his knowledge. One such areas….is his knowledge of the short-term interest rate trades, the STIR trades…
He seemed to suggest that the SFO were aware of the limits on his expertise, but when McLaughlin gave evidence, he said that he had not been present at any conversation when Rowe said that he was not qualified to give an opinion, or that he refused to look at documents because they were outside his expertise….
….when he was cross-examined by Mr Darbishire, he accepted what perhaps he should always have accepted, that some of the things he was being asked about were beyond his expertise, in particular in relation to STIR traders.
It follows that you ought to be very careful indeed before relying on his evidence on the topic, and you may think it safer to ignore it…..
On the other hand, there are other areas in relation to general banking, of which he has given evidence, and which are not really in dispute where you might find his evidence of use, and that will be for you to determine.”


One can be a little suspicious when the phrase “put bluntly” appears in a judgment. However this is definitely blunt.

  1. Put bluntly, Rowe signally failed to comply with his basic duties as an expert. As will already be apparent, he signed declarations of truth and of understanding his disclosure duties, knowing that he had failed to comply with these obligations alternatively, at best, recklessly. He obscured the role Mr O’Kane had played in preparing his report. On the material available to us, 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, most charitably, at the outer edge of his expertise) – a matter glaringly revealed by his need to consult Ms Biddle, Mr Zapties and Mr Van Overstraeten. In this regard, he was no more than (in Bingham LJ’s words) an “enthusiastic amateur”. He flouted the Judge’s admonition not to discuss his evidence while he was still 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 here for the consideration of others.



  1. The instruction of Rowe turned into an embarrassing debacle for the SFO, all the more so, given the high-profile nature of these cases and notwithstanding that, in the event, it has had no impact on the outcome in this case. We pressed Mr Hines as to whether there was an internal report, dealing with lessons learnt. We subsequently received a helpful letter from the SFO’s General Counsel, dated 27th November 2017, stating that there was no such document but that there had been extensive internal discussions resulting in the conclusion “…that Rowe’s conduct resulted from a failure of integrity on his part rather than a failure of SFO policies or procedures”. The SFO undertook to look again at the matter to see whether there was any way in which it could reinforce expert witnesses’ awareness of their obligations under the Crim PR.
  2. In fairness to the SFO, this was the third time that Rowe had given evidence in LIBOR trials and the first time any questions concerning his expertise had apparently arisen. Nonetheless, 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’ expertise and to engage (difficult though it sometimes may be) an expert of a suitable calibre.