Computer hacker Gary McKinnon is waiting with "anxiety, but hope" that Home Secretary Theresa May will halt his extradition to the United States and uphold promises made in Opposition, his lawyer has said.
McKinnon, who faces trial in the US over hacking into military computers more than 10 years ago, will find out tomorrow if Mrs May will offer him a last-minute reprieve.
McKinnon, who suffers from Asperger syndrome - a high-functioning form of autism - has been fighting against extradition for more than a decade and is waiting "with anxiety, but hope" for the decision, his lawyer, Karen Todner, said.
Prime Minister David Cameron and his deputy, Nick Clegg, have previously publicly condemned plans to send McKinnon to the US.
There has also been a long-running campaign for McKinnon to be allowed to remain in the UK following warnings from medical experts that he could kill himself if sent to the US to face trial.
Ms Todner said: "It has been a long 11-year battle to fight this extradition and we wait with anxiety, but hope, that the Home Secretary will uphold the promises previously made by Mr Cameron and Mr Clegg.
"We hope that our elected Government will uphold the promises they made whilst in Opposition and will prevent Mr McKinnon's extradition to America."
Marking the 10th anniversary of his first arrest earlier this year, McKinnon's mother, Janis Sharp, said the treatment of her son, who admits hacking into military computers but claims he was looking for evidence of UFOs, has been "barbaric".
He is "unable to control the terror that consumes his every waking moment", she said.
"What it’s been like is waterboarding of the mind,” she told the Telegraph.
McKinnon's legal team hopes Mrs May will block extradition amid predictions that he could be jailed for 60 years in America.
Medical evidence shows the 46-year-old is "suffering from a serious mental disorder and there is a serious risk of suicide if extradited", his legal team has said.
McKinnon, from Wood Green, north London, was arrested in 2002, and then again in 2005, before an order for his extradition was made in July 2006 under the 2003 Extradition Act.
That triggered three successive applications for judicial review and questions about the fairness of the UK-US extradition treaty, which critics claim is "one-sided".
An independent review of the UK's extradition arrangements by Sir Scott Baker last year found the current treaty between the US and the UK was both balanced and fair.
But the Government is under pressure to ignore its findings after MPs called on ministers to bring forward new laws and attempt to change the UK-US extradition treaty.
In a House of Commons debate in December, Tory MP Dominic Raab said: "Gary McKinnon should not be treated like some gangland mobster or al Qaida mastermind."
If Mrs May decides to allow extradition to go ahead, McKinnon's lawyers are expected to launch a last-ditch application for judicial review to challenge the decision.
A provisional hearing date has been set in the High Court for November 28 and 29.
McKinnon refused over the summer to undergo further medical tests by a Home Office-appointed expert during his battle to avoid removal.
Michael Caplan QC, an extradition specialist at Kingsley Napley LLP, said the extradition arrangements should be changed to enable the UK courts to decide where best to try a case.
"Whatever the Home Secretary's decision tomorrow, in my view there's a clear case for legislative amendment to include a forum test by the courts to determine the fairest jurisdiction for trial," he said.
"It should be for a British judge to hear all the arguments in favour of domestic prosecution and balance those against the requesting country's application for extradition.
"He will have in mind where most of the conduct took place and where the trial should take place in the interests of justice.
"A forum test could prevent the delays and controversies we have seen in recent extradition cases."
Melanie Riley, of the campaign group Friends-Extradited, said: "The strength of feeling on this issue is overwhelming.
"Britain was sold a pup in 2003 - it's time for this Government to right the wrongs."
McKinnon's 10 years "spent living on a knife-edge has been nothing short of cruel and unnecessary punishment", she said.
Ms Riley went on: "Extradition should not be determined on the mercy of the sitting Home Secretary or through horse-trading between US and UK prosecutors behind closed doors - this leads to delayed, arbitrary and, above all, populist not principled decision-making.
"Instead, there should be a swift and transparent examination of all matters affecting jurisdiction, determined by a judge in a British court, before any extradition of any British citizen is granted."