The family of two brothers jailed for murder are calling for the prosecution of a witness who admitted lying on oath during their trial.
They also want the man prosecuted for blackmail, claiming that after their trial he asked for £100,000 in return for him admitting to the authorities that he had lied.
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David and Ashley Cohen were jailed for 64 years between them in April 2008 over the murder of Sheffield taxi driver Younis Khan.
The 53-year-old was shot dead in his cab in Scott Road, Pitsmoor, in 2007, in what South Yorkshire Police said was a revenge attack after the taxi driver's son, Imran, fired shots at David's house.
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David, now 38 and formerly of Philadelphia Gardens, Upperthorpe, was jailed for 31 years and Ashley, 35 and formerly of Clough Wood View, Oughtibridge, was sentenced to 33 years.
The brothers, who have always maintained their innocence, were convicted on a joint enterprise basis in that the police claim they planned the shooting. It was never determined who pulled the trigger of the gun used in the attack.
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Murder trial witness Vincent Simmons, who was on remand at Armley Prison in Leeds while the Cohen brothers were waiting for their case to reach court, told jurors that he made notes in his prison cell of conversations with the pair.
Simmons, who was facing deception and money laundering charges at the time, claimed he was told ‘the whole thing had got out of hand’ and the brothers had only wanted people ‘frightened’.
During the murder trial, Simmons claimed to have taken his notes in the ‘interests of justice’.
He avoided a prison sentence when his own case reached court because of his 'public service' in giving evidence against the brothers.
But in recorded telephone calls made to the Cohen brothers’ family, he claimed the evidence he provided was false and asked for £100,000 in return for him making an on-camera confession in front of lawyers.
The Criminal Cases Review Commission, which examined the case after the emergence of the tape recordings, found the calls were made by Simmons but ruled against referring the case to the Court of Appeal, claiming there was 'no real possibility of the conviction being overturned'.
David and Ashley's mum, Pat Sharp, from Upperthorpe, who took one of the phone calls from Simmons, has reported him for blackmail to South Yorkshire Police.
She lodged her complaint on Thursday, May 31 but said nobody from the force has contacted her yet to arrange an interview.
"I am hoping that if the police investigate him for blackmail that the truth will come out," she said.