Mo said Liu agreed to the new legal challenge during a prison visit by his wife in October. Mo said he and a fellow lawyer have asked to meet Liu to discuss details but are awaiting permission from the local jurisdiction in China's northeast where Liu is locked up.
"He has never accepted the guilty verdict," Mo said.
Since Liu's incarceration, his wife Liu Xia has been placed under strict house arrest, but she was able to meet lawyers during the trial of her brother and it was then that she recruited Mo and Shang Baojun to prepare a petition for her husband's subversion case to be retried.
Family friend Hu Jia said the chances of a successful challenge are almost zero, but that supporters hope the challenge could allow lawyers to visit Liu and open a new channel of communication with him.
Liu apparently is under a restrictive watch to limit his knowledge of the outside world, and to prevent details of him from leaking out, Hu said.
For example, Liu Xia was banned from informing her husband of her brother's conviction and was able only to refer to it euphemistically by saying "he can no longer make money," Hu said.
Mo said the challenge could test Beijing's pledges last week to grant more independence to the country's courts.
"We would like to know whether Liu's Charter '08 was an exercise of freedom of speech and whether that constituted a crime," Mo said. "With outside intervention excluded, the conclusion should be obvious."
