ST. PAUL (AP) — A Ramsey County judge has found a 21-year-old St. Paul man not guilty of murder due to mental illness after he admitted strangling his mother and setting her duplex on fire.

Michael Ray Caldwell was charged with second-degree murder last September. Caldwell confessed to the killing at a hospital after going there for a psychological evaluation the day after his mother, 49-year-old Lorine Mary Johnson, was found dead.

Investigators found Johnson's body in a bedroom after neighbors reported the fire. Caldwell admitted that he argued with his mother about insurance money before he strangled her and lit the fire.

Before her death, Johnson and her boyfriend had flown to Kansas City to get Caldwell from a mental institution.

Judge George Stephenson issued his verdict Tuesday.