A former Barclays trader has failed in his bid to overturn a conviction for rigging the Libor interest rate – however prosecutor the Serious Fraud Office has come in for criticism regarding one of its expert witnesses.

In judgment handed down today in R v Alex Julian Pabon the Court of Appeal dismissed Alex Pabon’s appeal but said the SFO’s decision to call ex-trader Saul Haydon Rowe as a witness turned out to be an ‘embarrassing debacle’ for the office.

In 2016 Pabon was jailed alongside three other traders for conspiracy to defraud. He was released last year. 

Pabon, represented by London firm IBB Solicitors, argued that the evidence Rowe gave during his initial trial was incomplete or inaccurate and could have damaged his credibility.

On appeal, Lord Justice Gross, Mr Justice Sweeney and Mr Justice Haddon-Cave said that although Rowe’s evidence had ‘significant failings’ it had ‘no impact on the outcome of the case’.

Rowe was paid by the SFO to give evidence in Libor prosecutions. He also provided an expert report to the office on the workings of an investment bank and inter-dealing brokerage. His failings, according to the court, included obscuring the role of others during the prosecution and not informing the SFO or court of the limits of his expertise.

But giving the lead judgment, Justice Gross said: ‘We do not think that Rowe impacted at all or sufficiently on the key issue in the trial so as to affect the safety of the appellant’s conviction.’

However, he added: ‘The instruction of Rowe turned into an embarrassing debacle for the SFO, all the more so, given the high-profile nature of these cases.’

The court noted that 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,’, the judgment stated, ‘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.’

A spokesperson for the SFO said: ‘We are studying the judgment carefully and note that the court found the conviction to be safe.’