SYCAMORE, Ill. (AP) — A northern Illinois prosecutor wants a judge to have a special prosecutor investigate possible misconduct involving a murder case in the 1957 slaying of a 7-year-old girl.

The (DeKalb) Daily Chronicle reports that DeKalb County State’s Attorney Richard Schmack said in a Monday court filing that the special prosecutor should look into whether a Seattle police detective committed perjury in the prosecution of Jack McCullough for Maria Ridulph’s killing.

McCullough was convicted of the crime in 2012 but released earlier this year after Schmack said a review found flaws in the case and determined McCullough’s alibi was solid.

Schmack says a special prosecutor is needed because his office would be involved.

A Seattle police spokesman said the officer involved retired in 2013. They had no further comment.