Maria Ridulph, 7, was abducted while playing with a friend near her home in December 1957.
Her body was discovered months later in Jo Davies County.
Suspect Jack McCollough was 17 years old at the time and lived near Ridulph's home. New evidence allowed police to charge him with the crime. He was arrested last year in Seattle and brought to Illinois. He has pleaded not guilty.
It's one of the nation's oldest cold cases, something which can present problems for attorneys. For one, memories have faded. Prosecutors' case is largely based on circumstantial, or non-physical, evidence.
McCullough's attorney, Tom McCulloch, says the case is challenging.
(The Associated Press contributed to this report.)