Hayes was sentenced to 14 years in jail in August 2015 – later reduced to 11 - after being found guilty of eight counts of conspiracy to defraud. He was the first person in the UK to be convicted of rigging Libor.
He appealed his sentence in March 2016 after six former brokers alleged to have been his co-conspirators were found not guilty in a separate trial. This appeal was denied.
“I was prevented from using my co-defendants’ evidence to support my case,” he wrote. “My co-defendants were all acquitted… Various other people I was accused of conspiring with have been cleared. It appears that I have been convicted of conspiring with myself.”
Hayes also pointed to evidence that he said his defence team was not allowed access to, which showed that Libor manipulation was both widespread and condoned by the banks he worked for. Yet none of his managers had been made to face criminal charges.
Hayes has appealed to the Criminal Cases Review Commission, which looks at miscarriages of justice, claiming he did not receive a fair trial.
The appeal raises concerns over the fairness of his trial, given his Asperger’s syndrome diagnosis.
Hayes’ solicitor Karen Todner said she is confident the appeal will be successful.
She added, “It has been a lengthy and complex process to compile the application. It is clear from the evidence I have obtained that Mr Hayes has been the subject of a gross miscarriage of justice and I am confident that the CCRC will agree and refer the case back to the Court of Appeal.”
Todner said leading experts on Asperger’s syndrome support the view, and jointly said, “Mr Hayes conviction raises real concerns about the treatment of autistic people in the criminal justice system”.
Todner added, “In addition I believe there has been material non-disclosure of key items of evidence that were withheld from the defence at the original trial, which will now throw a whole new light on Mr Hayes’ case.”
Hayes joined UBS in 2006 and became a senior trader in interest-rate derivatives indexed to yen-denominated Libor. He contributed almost $260m in revenues over the three years before he left the bank to join Citigroup.
The prosecution said that while he was there he had conspired with rate setters and traders both at UBS and other banks represented on the panel that set the Libor daily rate, to move the rate up or down in order to benefit his trading positions.
After leaving UBS, he continued his activities at Citigroup until the bank found out about the rigging and sacked him.
UBS was fined millions of pounds over the role certain former employees played in rigging Libor, including £160m which it paid to the Financial Conduct Authority's predecessor body, the Financial Services Authority.
The Serious Fraud Office (SFO) arrested Hayes in December 2012 and he was charged with eight counts of conspiracy to defraud in June 2013.
From December to June, Hayes gave 82 hours of taped interviews confessing to trying to persuade others to rig the benchmark rate.
He later retracted the confession and changed his plea to not guilty claiming he was frightened of being extradited to the US and had only confessed so he could face trial in the UK.