Peng was imprisoned for the rest of his life. In 1969, the party formed a "special investigation group" to reach a verdict in his case. Peng's jailers then forced him to write a full biography of his life many times, but they did not believe that he ever fully confessed his "crimes." Peng was then subjected to constant violent "interrogations" throughout most of 1970 until a special military tribune sentenced Peng to life imprisonment. The sentence was immediately approved by Lin Biao's General Chief of Staff, Huang Yongsheng.