A psychiatrist who treated Colorado theater shooter James Holmes is expected to testify against him in his death penalty trial.

Prosecutors say they will call Lynne Fenton to the stand on Tuesday. Her testimony is among the most highly anticipated, as she was the mental health professional with the most access to Holmes' mind before he opened fire on a crowded movie theater, killing 12 and injuring 70. It could help answer lingering questions about what she did after Holmes told her he was having thoughts of killing people.

She told a campus police officer about her concerns in June 2012, a month before the attack.

A lawsuit against Fenton and the University of Colorado says she refused an officer's offer to place Holmes on a 72-hour psychiatric hold.