Gary McKinnon could face up to 70 years in a US prison
Human rights campaigner and former hostage Terry Waite has called on the US to drop charges against British computer hacker Gary McKinnon.
Glasgow-born Mr McKinnon, 42, from Wood Green, north London, faces up to 70 years in prison if found guilty in the US of breaking into military computers.
He has Asperger's Syndrome and claims he was looking for details of UFOs.
Mr Waite, a hostage in Lebanon for four years, called the motives "harmless" and said "common sense" was needed.
He said the Pentagon ought to thank the self-confessed hacker for "exposing" the vulnerability of its computer security.
Mr Waite said Mr McKinnon's illness, a form of autism, made him "irrationally obsessive" and added that it was a waste of time to pursue him.
"No nation under the sun ought to convict an individual whose behaviour is occasioned by illness," he said.
"Gary is clearly a very clever chap.
"He has that unique ability to find his way through the internet jungle and enter the inner recesses of the Pentagon. Full marks for his ingenuity.
Campaigner Terry Waite was held hostage for more than four years
"Was Gary a spy? Was he attempting to bring down the mighty military force of the USA? As far as I know he was not. He was simply looking for little green men.
"Anyone who has the slightest acquaintance with [Asperger's Syndrome] will know that while the sufferer can be, and indeed often is, brilliant in certain logical processes they can become irrationally obsessive in other directions."
However, Mr Waite - who was kidnapped in Lebanon in 1987 - said he supported the efforts of the authorities to "track down and stop illegal activity" on the web.
Mr McKinnon's lawyers have appealed for him to be prosecuted in the UK on lesser charges, but the CPS said the best place for the case to be heard was the US.
In total, he hacked into 97 government computers belonging to organisations including the US Navy and Nasa during 2001 and 2002.
The US government says this caused damage costing $800,000 (£550,000) at a time of heightened security in the wake of the 11 September 2001 terror attacks.
Mr McKinnon, who was arrested by British police in 2002, has already appealed unsuccessfully to the House of Lords and the European Court of Human Rights to avoid extradition.
His battle now rests on a judicial review of the government's decision to extradite him. His lawyers have claimed he is at risk of suicide if extradited.