Britons extradited to the United States have no chance of being cleared as the plea bargaining system empowers prosecutors as "judge, jury and executioner", one of the NatWest Three said today.
David Bermingham, who was one of three bankers jailed for 37 months over an Enron-related fraud in a deal with US prosecutors in 2008, said no sane defendant would risk dozens of years in jail when a plea bargain could enable them to be home within months.
Plea bargaining is common in the US, with defendants often able to secure a more lenient sentence if they admit an offence and co-operate with prosecutors, rather than contest the charges in a trial.
But the system, and the pressure it places on defendants, leaves those extradited to the US from the UK with little choice but to accept a deal if they want to return to their families at home, Bermingham claimed.
"A prosecutor can now effectively be judge, jury and executioner," he said.
"He can say, 'I'm going to charge you with 98 different counts, each carrying a five or 10 year maximum sentence, and potentially you could be sentenced to literally the rest of your life in prison'.
"And there's no parole. There's no two ways about it.
"A prosecutor can threaten a defendant with the rest of his life in prison. However if you are willing to plead guilty, 30 years becomes five years.
"If you are then co-operating and willing to give evidence against others, five years becomes two."
US prosecutors often quote maximum sentences, rather than the most likely jail term, for each offence, in part to act as a deterrent to others.
But Bermingham, 49, of Goring, south Oxfordshire, said negotiating the US system was akin to "game theory".
"Do I sell my soul and all my principles in order to get my lenient sentence, or do I risk a trial and being jailed for life?"
Bermingham spoke out as his book, A Price To Pay, was published today as retired British businessman Christopher Tappin is held at the Otero County detention centre in New Mexico awaiting trial over arms dealing charges in El Paso, Texas.
"The Chris Tappins of this world have no reasonable prospect of ever being able to defend his case," Bermingham said.
"Imagine how difficult it is to try to defend a white collar case when you can't even stay in the same room as your lawyer."
He added that prosecutors could also help ensure that a defendant who agrees to a plea deal is sent back to the UK, whereas those who risk a trial would serve all of any sentence in a US prison if found guilty.
And the cost to a defendant of taking a case to trial was also prohibitive for most people, he claimed.
"What sane man in this case is going to say anything other than, 'Where do I sign?'" he said.
"Some people say that's expeditious justice and there's no smoke without fire."
But he added it was "not a justice system which we would necessarily want to associate ourselves with" as it virtually guaranteed that extradited Britons would return as guilty.
"What it boils down to is the US criminal justice system is a very difficult place for defendants anyway," he said.
"Over the last 20 years the prosecutor has become more and more powerful, there are more and more powers at his disposal to ensure the outcome of any given case is a plea bargain rather than the case going to trial."
A US Embassy spokeswoman said: "Similar to the UK system, US criminal defendants in appropriate cases are able to receive reduced sentences by pleading guilty at an early stage of the judicial process.
"US prosecutors are authorised to offer individuals who have been arrested and charged with a crime the option to plead guilty before their cases proceed to trial.
"A judge must always approve such agreements or 'plea bargains' before they can be concluded.
"The court approval process includes a personal appearance by the defendant before the judge in which the defendant admits under oath that he or she committed the crime in question and confirms that he or she is pleading guilty voluntarily."
She added that the system was "intended to allow defendants who accept responsibility for the crimes for which they are accused to receive credit for that acceptance of responsibility by obtaining lower sentences".
The spokeswoman went on: "Most sentences, both in cases that are resolved by guilty pleas and cases that proceed to trial, are significantly less than the maximum sentence available under law.
"In any criminal case, in order to protect persons who are wrongly accused, the government must prove the accused is guilty 'beyond a reasonable doubt' - the highest standard of proof - and the jury must be unanimous in order to find a defendant guilty.
"As a result of this high standard of proof, defendants are found 'not guilty' every day in US courts."