REPRIEVE, US has given more details about this case http://www.reprieve.org/ali-al-nimr.html
Some quotes from there: “He was accused of participation in an illegal demonstration and a large number of other offenses. These include “explaining how to give first aid to protestors” and using his blackberry to invite others to join him at the protest…….Ali was tortured and forced to sign a false confession. This was the only evidence brought against him. He was sentenced to ‘death by crucifixion,’ which in Saudi Arabia involves beheading and public display of the body……Ali’s final appeal was held in secret, without his knowledge. This was the last remaining legal obstacle to his execution, and now Ali can be crucified at any time……Ali was arrested without a warrant. He was held in pre-trial detention for two years, and at no point was he allowed to contact his lawyer. Ali was tortured and forced to sign false confession. Throughout his trial, Ali was denied access to the evidence against him. He was not even informed of the charges until half way through the proceedings. His forced confession was the only evidence brought against him. He was sentenced to ‘death by crucifixion’…….Ali’s final appeal was held in secret, without his knowledge. This was the last remaining legal obstacle to his execution, and now Ali can be crucified at any time. The authorities may not even give prior notification of his family. His execution would be illegal under international law.”