The latest parole hearing for John Lennon's killer has been postponed, delaying Mark David Chapman's sixth bid for freedom. The 55-year-old was scheduled to appear before a parole hearing this week at the Attica correctional facility in New York, where he has served 29 years. But the appointment could not take place because the parole board said it was awaiting additional information to complete Chapman's record.

Chapman shot and killed Lennon outside an apartment building in New York in 1980. Though his lawyers wanted to enter a plea of not guilty by reason of insanity at the original trial, Chapman pleaded guilty to second degree murder and was sentenced to 20 years to life in prison with psychiatric treatment. Infamously, Chapman showed an obsession with the JD Salinger novel The Catcher in the Rye and read an excerpt from the book at his trial.

Chapman has been imprisoned since 1981 and has been denied parole five times since October 2000. Lennon's widow, Yoko Ono, has repeatedly campaigned against the possibility of parole for Chapman, recently saying she still feared for the safety of herself and her sons should he be released.

Chapman's parole hearing will now take place in September.