Jack McCullough, 76, was sentenced to life in prison in 2012 following his conviction in one of the oldest unsolved US cases to go to trial. Maria Ridulph was abducted in 1957 as she played in the snow near her home in Sycamore, Illinois, about 65 miles west of Chicago. Her remains were found five months later by hikers.

A judge has now ordered Mr McCullough's release based on newly discovered phone records that supported his long- held contention that he was about 40 miles away on the day Maria disappeared. The new evidence was found during a review of the trial by DeKalb County State's Attorney Richard Schmack. Mr Schmack wrote in his findings that documents he found contained "a wealth of information pointing to McCullough's innocence, and absolutely nothing showing guilt".

At trial, prosecutors alleged Mr McCullough was the man who approached Maria and her friend on 3 December 1957, identifying himself as "Johnny". When the friend returned from retrieving mittens from her home nearby, the man and Maria had vanished. Mr McCullough, who went by the name John Tessier in his youth, was one of nearly 100 people suspected by police at the time. He was not arrested based on what was thought to be a solid alibi.

The then-19-year-old contended he was in Rockford that day attempting to enlist with the US Air Force. Authorities went after Mr McCullough again some 50 years later after his half-sister, Janet Tessier, said Mr McCullough's mother made incriminating comments about him just before her death in 1994. During a follow-up investigation, Maria's childhood friend identified Mr McCullough as "Johnny" from an old photograph. On Friday, Judge William Brady made clear his decision to free Mr McCullough was not a new verdict in the case.

He said: "Rest assured I am not trying this case ... You will not hear the words, 'Mr McCullough is guilty' or 'Mr McCullough is not guilty' coming from my mouth." Maria's family said they remain convinced the girl's killer is Mr McCullough, who lived most of his adult life in Washington state, where he worked as a police officer. Maria's brother, 70-year-old Charles Ridulph, told local media the family feels let down by the prosecution office's about-face.