Complex sentence: Banas stated that he did not interview Grills because, at the time, she was under psychiatric treatment for the involvement in the Meier case, and did not plan to interview her at a later date.
Split into simpler sentences: Banas stated that he did not interview Grills because, at the time, she was under psychiatric treatment for her participation in the Meier case. He did not plan to interview her at a later date.