A 76-year-old Washington state man released from prison after a prosecutor concluded he was wrongly convicted in the 1957 killing of a schoolgirl says he intends to sue Illinois.

Jack McCullough spoke to The Associated Press on Sunday, two days after a judge vacated his 2012 conviction in the slaying of 7-year-old Maria Ridulph in Sycamore, Illinois.

He says about his imprisonment: "They didn't just punish me — they punished ... my whole family."

McCullough spoke from an acquaintance's home outside Sycamore. He says while behind bars, he wrote letters to state officials and the president pleading them to intervene. He says those messages went unanswered.

DeKalb County's current state's attorney has called the investigation of McCullough deeply flawed. McCullough says investigators wanted to boast they'd solved one of the oldest cold cases in the country to go to trial.