Peter Howson, one of Britain's most celebrated artists, will complete a series of portraits of Gary McKinnon this month, to highlight the case of the UFO enthusiast who faces ten years in a US jail after hacking into the American Army's computer network, causing it to crash.

Mr McKinnon - who is originally from Glasgow - faces a final judicial review of his extradition in two weeks, after which he could face charges relating to almost 100 offences.

Like Howson, he has Asperger's syndrome, a form of autism that often makes it hard for sufferers to express themselves, causing some to focus their energy on one subject, to the exclusion of all others. It is often associated with people of higher than average intelligence.

The artist said that his subject should be treasured for his “obsessive brilliance” rather than thrown in jail, and compared Mr McKinnon to Alan Turing, the loner who became the master code-breaker of the Second World War. Turing cracked the Nazi Enigma code, an extraordinary intellectual feat held by many historians to have been a turning point in the war.

“Twenty years ago the Americans probably would have employed someone like Gary, rather than calling for his head on a platter,” Howson said. “His only crime is an over-zealous inquisitiveness in flying saucers and he just got carried away. He is an obsessional person, but also an exceptional person.

“Turing had a sad, tragic life, but he was brilliant at breaking codes. In the same way Gary has this amazing gift and it should be nurtured. If he ends up going to prison, I don't think it will be possible for him to cope at all. This will be a massive, overwhelming tragedy in his life.”

Mr McKinnon, 42, an unemployed systems analyst, is said by US prosecutors to have become the most successful computer hacker in history when he accessed 97 computers at the North American Space Agency in 2001 and 2002, causing an estimated £500,000 of damage. He has admitted the offences. He was subsequently diagnosed with Asperger's.

Last year Mr McKinnon failed to have his extradition overturned in the High Court and the House of Lords. His parents, Charlie McKinnon and Janis Sharp, have launched a last-ditch attempt to prevent a trial in America.

Howson said that he had been approached by the McKinnons in November to help in their campaign and had not hesitated to offer assistance. Working from photographs, he has made drawings and oil sketches of Mr McKinnon, some of which include images of flying saucers. He is currently working on a sequence of paintings, which he hopes to complete within the next two weeks.

“The thing about Asperger's is that if you are going to do something, you are going to go deeply into it. So deep that it might get you into trouble without you really knowing about it. I know people who have the condition who forget everything else - washing, dressing. Everything is geared towards one thing, one gift they have,” Howson said.

Mr McKinnon broke into US military systems from a PC in his bedroom in North London, and from a computer in his girlfriend's aunt's house. Known online as Solo, he said that he was trying to expose security weaknesses and uncover evidence of UFOs. He is also alleged to have shut down 300 computers at a navy weapons station immediately after the terror attacks of September 11, 2001.

“I was a man obsessed,” Mr McKinnon wrote last year, describing a year spent trying to break into US military systems, efforts which were fuelled by beer and marijuana. In interviews, he claimed that his hacking had uncovered photographic proof of alien spacecraft and the names and ranks of “non-terrestrial officers”.

Howson came to public attention when in 1993 he was chosen as the official British war artist in Bosnia.

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