Paul Vallely: Our extradition treaty is plainly unjust

The number of British citizens in US jails shows how lopsided is the current arrangement between this country and America

Remember the NatWest Three? They were the British bankers known for their long fight against extradition to the United States to face charges of helping construct some dodgy deals which played a tiny part in what was, in 2001, the biggest bankruptcy scandal in American corporate history. One of them had a book out last week. It was big on indignation at the whole extradition business and rather less outraged about the $7.3m fraud to which they pleaded guilty when they finally got to a US courtroom. Funny that.

A couple of days later, extradition was back in the headlines when the High Court temporarily blocked the removal from Britain of the British businessman accused of arranging the contract killing of his bride on their honeymoon in Cape Town in 2010. Two judges ruled that it would be "unjust and oppressive" to order the man to face trial in South Africa because he is mentally unfit.

It is as well to remember those cases when reflecting on the new Home Affairs Select Committee report which says an overhaul in UK extradition laws are needed to restore faith in the system. Of particular concern, it says, are the lopsided arrangement with the United States which mean it is "easier to extradite a British citizen to the USA than vice versa".

There have been several cases which give cause for concern. Christopher Tappin, a 65-year-old retired businessman from Orpington, is facing a 35-year sentence for allegedly selling batteries that would ultimately end up in Iranian missiles. A 23-year-old Sheffield student, Richard O'Dwyer, is fighting extradition on charges of infringing US copyright on the website he ran in the UK. And Gary McKinnon, who has Asperger's syndrome, has been fighting extradition for 10 years after he hacked into the Pentagon computer system looking for info on UFOs.

The American ambassador Louis Susman warned the MPs against viewing the UK-US extradition treaty "through the prism of individual cases where sentiment and emotion can cloud reality and lead to misrepresentation". The system was fair, balanced and "promotes the interests of justice in both our countries", he insisted. He is wrong.

Extradition is a necessary part of international law. Without it, Britain would become a haven for criminals seeking to evade justice. The rapid growth of the internet, organised crime and international terrorism mean we need effective extradition arrangements with other countries.

Yet there are big problems with the present set-up. One is the legal asymmetry of the UK and US systems. For an American to be extradited to Britain, the US courts have to examine the evidence to ensure that extradition does not violate the suspect's rights under the fourth amendment to the US constitution. That says US citizens cannot be arrested unless the authorities have "probable cause". But under the 2003 extradition treaty, a British court merely has to accept that US prosecutors have a "reasonable suspicion". Lawyers disagree on how substantial this difference is, though when the law was being passed a Home Office minister, Baroness Scotland, told the House of Lords that Washington demanded "a higher threshold" than London would.

There are also questions of natural justice. Gary McKinnon, with his Asperger's and risk of suicide, shows that compassion must be a mitigating factor. So must jurisdiction; Richard O'Dwyer's offending website was not located in America. Their activities would not have been regarded with the same gravity in the UK, and may not even have amounted to a crime at all. "If he has questions to answer," said David Cameron of McKinnon, "there is a clear argument to be made that he should answer them in a British court." But that was before Cameron became Prime Minister.

There are issues too about the quality of foreign legal systems. Christopher Tappin claims he was the victim of entrapment by US law enforcement agencies acting unlawfully. Andrew Symeou was extradited to Greece in 2009 to face manslaughter charges over a nightclub death where evidence against him had been obtained by Greek police officers intimidating witnesses. Edmond Arapi, an Albanian from Staffordshire, was served an extradition order by Italy the same year in a case of mistaken identity.

Questions of proportion are important too. Babar Ahmad, an IT worker from Tooting, has been held in a British jail for more than seven years while contesting extradition to the United States. He is accused by the Americans of running online fundraising operations for jihadists in Chechnya and Afghanistan. Yet Scotland Yard had earlier arrested and released him without charge. Not only has he not been tried in the UK but he has been detained for an exorbitant length of time.

Extradition is often a punishment in itself, even for those who are eventually acquitted. Andrew Symeou spent 10 months in a Greek prison before the case against him collapsed. Those extradited are taken from their home, family, job and community. They are jailed in a foreign country and, often, language, which may well also impede their ability to mount an effective defence. They can, as Gary McKinnon's mother put it, also lose their sanity or even their life.

Not all those extradited are innocent, as the case of the NatWest Three shows. And the existing system does not entirely lack flexibility, as the Cape Town murder case reveals. But British judges need powers to halt extradition until they are satisfied that a foreign court is ready to try a suspect so they do not spend years in detention with no trial date fixed, as is now the fate of Christopher Tappin in Texas. They should have the authority to insist that a defendant be tried in the UK where two jurisdictions are involved. And they should be empowered to ascertain that there is a genuine prima facie case to answer before anyone is sent abroad. One of the primary duties of any government is to protect its people. The present extradition arrangements do not do that properly.