OBERLIN — An Oakdale man accused of fatally stabbing his neighbor in April has pleaded not guilty by reason of insanity.

Ralph Johnson, 61, faces charges of second-degree murder and obstruction of justice in the slaying of Michael Kirklin, 21. The two lived in the same apartment complex, authorities said.

Johnson, who was indicted in May, pleaded not guilty by reason of insanity in June.

District Attorney Todd Nesom said this week that a sanity investigation has been ordered to determine whether Johnson was insane at the time of the slaying.

An insanity defense requires a finding that the person suffers from a severe mental illness and cannot distinguish between right and wrong.

Police were called to the Bowman-Hicks apartments on Harvey Street in reference to a man with a knife threatening to kill people, authorities said. When officers arrived, they learned that Johnson had stabbed Kirklin during an altercation, police said.

Witnesses told police, Kirklin was trying to defend his grandmother after Johnson attacked her. The grandmother suffered a cut to the finger.

During the altercation, Johnson allegedly cut Kirklin several times on the face before stabbing him in his left side. Kirklin was taken by a personal vehicle to the Oakdale hospital, where he was pronounced dead.

A knife fitting the description of the one used in the stabbing was recovered from Johnson’s residence during his arrest. Johnson remains in the Allen Parish jail pending the sanity hearing.