Computer hacker Gary McKinnon is due to find out whether Home Secretary Theresa May will end his 10-year battle against extradition to the United States.
The ups and downs of his fight have been so cruel they amount to "waterboarding of the mind", his mother Janis Sharp said.
She is hopeful that Mrs May will end her son's suffering by blocking his extradition to the US, where he is accused of "the biggest military computer hack of all time".
The 46-year-old who suffers from Asperger's syndrome - a high-functioning form of autism - admits hacking into US military computers but claims he was looking for evidence of UFOs. Home Office medical evidence shows he is very likely to try to kill himself if extradited to the US, where he faces up to 60 years in prison if convicted.
Ms Sharp said the US stance appeared to soften this summer, with government adviser John Arquilla saying the US should be recruiting elite computer hackers to launch cyber-attacks against terrorists instead of prosecuting them. She admitted she was "still scared" ahead of the decision.
"It's like waterboarding of the mind - you're elated, you're down, it's so cruel," Ms Sharp said, referring to the simulated drowning technique which became notorious after its use by CIA interrogators on Guantanamo Bay terror suspects.
Prime Minister David Cameron has raised McKinnon's case with US president Barack Obama twice "and each time I thought we were nearly home and dry but nothing happens", she added. "I'm more optimistic now. I don't see how they could say that in evidence and then extradite."
Both Mr Cameron and his deputy Nick Clegg have previously publicly condemned plans to send McKinnon to the US. 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.
McKinnon's lawyer Karen Todner said the Home Secretary only had limited discretion under the law to stop the extradition, telling BBC Radio 4's Today programme: "Theresa May can make a decision that if Gary is at extreme risk of suicide, that she can prevent his extradition and we have provided her with the medical report, which will allow her, within the law, to make that decision."
She added: "Gary is a classic computer nerd, he was looking for UFOs, that was what he was searching for."