LONDON—Lawyers for Tom Hayes, convicted in August as the mastermind of a global interest-rate-rigging scandal, argued Tuesday for his conviction to be overturned and his 14-year prison sentence to be reduced.

Mr. Hayes's lawyers appeared before a panel of three judges in the Court of Appeal. They argued that the judge in his trial, which ran for nine weeks over the summer, gave improper instructions to the jury and wrongly excluded certain evidence that would have helped the defense.

The defense also argued that the 14-year sentence, which trial judge Jeremy Cooke argued was necessary to send a deterrent message to the rest of the banking industry, was excessive.

The appeal is being heard by some of the U.K.'s most prominent judges, including John Thomas, the head of the judiciary for England and Wales, and Brian Leveson, who rose to fame by chairing a 2012 public inquiry into British media ethics. The third judge is Elizabeth Gloster.

Mr. Hayes, a 36-year-old Briton who worked for UBS Group AG and Citigroup Inc. in Tokyo, was the first person to be convicted by a jury for his role in rigging the London interbank offered rate, or Libor, and other widely used benchmark rates. Libor and its brethren serve as the basis for interest rates on trillions of dollars of loans and other financial contracts.

The 14-year sentence that Judge Cooke handed down in August was one of the stiffest in recent years for a white-collar criminal. The appeal is being closely watched not only because of Mr. Hayes's prominent role in the Libor-rigging scandal but also because British prosecutors are currently trying six of his alleged co-conspirators.

Lawyers say that an overturned verdict, or even a substantially reduced sentence, would deal a significant blow to the efforts of British fraud prosecutors to pursue such cases.

Mr. Hayes, an intelligent but socially awkward mathematician whom colleagues dubbed "Rain Man," was diagnosed earlier this year with Asperger syndrome, a mild form of autism. His lawyers and family members argued that the condition impaired his ability to understand that what he was doing was wrong, especially because his tactics were widespread in the industry at the time and there weren't laws explicitly prohibiting tampering with benchmarks like Libor.

The prosecution in Mr. Hayes's case, led by prominent British trial lawyer Mukul Chawla, argued that the defense was presenting nothing more than a smokescreen and that the ubiquitous nature of Libor-rigging didn't justify Mr. Hayes's actions.

The two-day appeal hearing—being heard at London's Royal Courts of Justice, a gothic-style stone courthouse with vaulted ceilings, marble floors and echoing hallways—was scheduled on an expedited basis, and lawyers say the panel could deliver its ruling within a few days.

Regardless of the outcome, the defense and prosecution can appeal to the U.K.'s Supreme Court.

Write to David Enrich at david.enrich@wsj.com

 

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(END) Dow Jones Newswires

December 01, 2015 06:35 ET (11:35 GMT)

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