McKinnon, 46, admits hacking American government computers attempting to find evidence of UFOs.
May indicated the only question shaping her decision was McKinnon’s human rights.
Based on the evidence before her it was her decision that McKinnon was too great a suicide risk to commit to trail in the US.
McKinnon suffers from Aspergers syndrome, a form of Autism.
May told MPs: “After careful consideration of all the relevant material I have concluded the Mr McKinnon extradition would give rise to such a risk of him ending his life that a decision to extradite would be incompatible with his human rights.”
However director of public prosecutions Keir Starmer would now decide whether McKinnon will face trial in the UK.
McKinnon’s mother, Janis Sharp, said: “Thank you, Theresa May, from the bottom of my heart. I always knew you had the strength and courage to do the right thing.”
One of the arguments McKinnon’s legal team used throughout his case was the notion that if McKinnon had committed a crime it was on British soil.
Shami Chakrabarti, director of Liberty said: “Extradition should prevent fugitives escaping – not allow for Britons like Gary to be parcelled off around the world based on allegations of offences committed here at home.”
However, writing on the New Statesman’s website, legal commentator, David Allen Green said if evidence before the Home Secretary pointed to a suicide risk, “then it was plainly the right decision for her to make, though it opens obvious questions as to whether it can be now a precedent for other extradition cases.
“It appears that, but for this determination, the extradition would have proceeded – put another way, the legal case for McKinnon’s extradition was otherwise sound.”
McKinnon was arrested in 2002 and again in 2005 for hacking 96 computers in five American government departments, described as the the “biggest military computer hack of all time”.
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