Krishna “Kris” Maharaj was a self-made millionaire, collected Rolls-Royces and was one of Britain’s biggest racehorse owners. Then he was convicted of a double murder he has always insisted he did not commit.

When he appears before a Florida judge this autumn, it will be the Briton’s best chance in almost 30 years to clear his name. At the climax of his 1987 trial, the Trinidad-born entrepreneur was sentenced to death for the double murder of his business partner Derrick Moo Young and Young’s son in a Miami hotel room.

Yet at an evidentiary hearing scheduled for the week of 10 November, lawyers for the 75-year-old will present compelling evidence that Mr Maharaj was framed. And in a plot that sounds plucked from the pages of an airport thriller novel, they intend to argue that the Youngs were killed by Colombian hitmen working for Pablo Escobar, the infamous boss of the Medellin drug cartel.

Before his conviction, Mr Maharaj had built a fortune in food imports and newspapers, and in the mid-1980s was living in Florida, where he invested in a property scheme with Mr Young, a Jamaican businessman. The partnership soured dramatically, however, when Mr Maharaj accused Mr Young of defrauding him to the tune of $400,000 (£250,000).

On 16 October 1986, Mr Maharaj went to the Dupont Plaza Hotel in downtown Miami and waited in room 1215 for a business associate who, he says, never turned up. His legal team claims Mr Maharaj was lured there to leave his fingerprints at the scene, and left before the Youngs arrived. Prosecutors said he lay in wait for Mr Young, 53, and his son Duane, 23, confronted them about the missing cash – then shot them both dead.

Later that evening, Mr Maharaj was arrested while eating dinner at a Miami restaurant with his wife, Marita. But the case against him was flawed from the start. He passed a lie detector test shortly after his arrest. Six witnesses placed him 25 miles from the crime scene at the time of the murders, though they were never called to testify.

Drug lord Pablo Escobar was behind the killings, according to Krishna Maharaj’s lawyers (Getty Images)

Instead, the jury heard from one Neville Butler, who claimed to have witnessed the killings – but who failed a lie detector test, changed his story several times and has since committed perjury in six court cases, according to lawyers for Mr Maharaj. As for the alleged motive, Mr Maharaj was suing Mr Young for the fraud at the time. In an interview with the Mail on Sunday, he later said, “If I’d wanted to kill him, surely I’d have waited until I got my money?”

The first judge at the trial was himself arrested for taking bribes after falling for an undercover sting by a Florida law enforcement officer posing as a cartel operative. The judge’s replacement, it has since been revealed, had the death penalty drawn up for Mr Maharaj before a guilty verdict was even delivered. Mr Maharaj would later tell CNN that as he entered the US penal system, perhaps never to emerge, “I went from living like a prince to existing like an animal.”

In 2001, British politicians including London Mayor Ken Livingstone, Lib Dem leader Charles Kennedy, and Lord Goldsmith – then Attorney General – signed a letter addressed to Florida governor Jeb Bush, citing the “astonishing flaws” in the case and calling for a retrial. The following year, Mr Maharaj’s death sentence was commuted to life imprisonment but subsequent appeals for clemency have failed.

Mr Maharaj has been represented since 1993 by Clive Stafford Smith, the UK legal director of the human rights charity Reprieve, who told The Independent: “There are two ways to prove you’re innocent. The first is proving exactly who did do it, which is very difficult – although in this case I think we can do that. But surely the second way is to ask whether any of the prosecution case is left. And there really is no case left against Kris Maharaj. To me that’s enough; we shouldn’t have to prove who really did it.”

And yet, Mr Stafford Smith and his colleagues suggest they have done just that, securing confessions from three Colombian former cartel members that the Medellin cartel was behind the killings. They also took statements from former Miami police officers and other law enforcers, who admit they helped in covering up cartel involvement and framing Mr Maharaj.

According to the new evidence, the Youngs had laundered as much as $5bn in cartel money in the Caribbean, but were also skimming some of the cash for themselves. That meant they had crossed Pablo Escobar, whose control of three-quarters of the Colombian cocaine trade had made him the world’s seventh richest man.

Former British millionaire Krishna Maharaj sits in prison in 2007 (AP)

Unbeknown to Mr Maharaj’s original defence team, just one other room on the 12th floor of the Dupont Plaza was occupied on the day of the murders. The guest in room 1214 – across the corridor – was Jaime Vallejo Mejia, a Colombian already wanted for his part in a cartel laundering case. The new evidence suggests Mejia was joined there by associates including hitman Guillermo Zuluaga, known as “Cuchilla” – “the Blade” – who carried out the murders at Escobar’s behest.

A former Escobar enforcer, known only as El Asistente, described the killings for Mr Maharaj’s defence, adding, “I have reconnected with my religious faith. The idea that Krishna Maharaj has served more than a quarter-century in prison for a crime I know he did not commit appals me.”

Zuluaga died in 1993, when he was kidnapped, tortured and dropped into a sugar cane threshing machine by members of a rival gang. Escobar was killed later the same year in a shoot-out with Colombian police. Mejia was deported from the US to Colombia, where he is under investigation for money laundering.

Mr Maharaj, meanwhile, has languished behind bars for 28 years, and two years ago came close to dying after he contracted necrotising fasciitis, a flesh-eating bacteria that had also afflicted the previous two occupants of the bed in which he caught it. The condition has left him largely confined to a wheelchair. His wife, Marita, lives in Fort Lauderdale, Florida. “I miss everything about him,” she recently wrote in a piece for the New Statesman. “In my small cottage, I never sit down for a meal without laying out a place setting for Kris. I always think that he might walk in the door.”

In spite of Mr Maharaj’s situation, Mr Stafford Smith said: “Kris suffers from terminal optimism. Every time we’ve had a hearing or appeal he’s convinced he’s going to win. When you’re innocent, it’s really hard to believe that 12 people will find you guilty beyond reasonable doubt. Kris began with a naive faith in the legal system, and he still has some of that.”

When the new evidence came to light, Florida prosecutors remained steadfast, claiming the defence team’s “fantastical allegations” were based on “hearsay and inadmissible evidence”. Even organising the hearing has been a hellish task for Mr Maharaj’s lawyers, who must marshal witnesses from across the world.