TULSA, Okla. (AP) - An attorney for an Oklahoma teenager charged along with his brother in the stabbing deaths of their parents and three siblings may seek an insanity defense.

Seventeen-year-old Michael Bever has pleaded not guilty in the July 2015 killings of their family members in suburban Tulsa.

The Tulsa World reports that Bever's attorney filed a notice of intent to raise the question of Bever's mental status at the time of the killings.