SPRINGFIELD, Mo. (AP) — Attorneys for a man charged with killing a retired Missouri State University professor say they will enter a new plea for the suspect.

The Springfield News-Leader reports attorney Dee Wampler will file a motion this week to change 44-year-old Edward Gutting’s plea from not guilty to not guilty by reason of mental disease or defect.

Gutting, an assistant professor at Missouri State, is charged with first-degree murder and four other felonies in the August 2016 death of professor Marc Cooper and the wounding of Cooper’s wife, Nancy.

A court hearing on the amended plea is scheduled for March 20.

Investigators say Gutting stabbed Marc Cooper to death and stabbed Nancy Cooper several time at the Coopers’ home. A motive has not been publicly disclosed.