Homicide

Suspect in Colorado theater shooting trial faces long odds with insanity defense

  • FILE - In this July 23, 2012 file photo, James Holmes sits in Arapahoe County District Court in Centennial, Colo. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Denver Post, RJ Sangosti, Pool via AP, file)

    FILE - In this July 23, 2012 file photo, James Holmes sits in Arapahoe County District Court in Centennial, Colo. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Denver Post, RJ Sangosti, Pool via AP, file)  (The Associated Press)

  • FILE - In this Jan. 20, 2015 courtroom file sketch, James Holmes, left, and defense attorney Tamara Brady are depicted, as they sit in court on the first day of jury selection in Holmes' trial, at the Arapahoe County Justice Center, in Centennial, Colo. Jan. 20, 2015. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Jeff Kandyba, file)

    FILE - In this Jan. 20, 2015 courtroom file sketch, James Holmes, left, and defense attorney Tamara Brady are depicted, as they sit in court on the first day of jury selection in Holmes' trial, at the Arapahoe County Justice Center, in Centennial, Colo. Jan. 20, 2015. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Jeff Kandyba, file)  (The Associated Press)

  • FILE - This file photo released on Sept. 20, 2012 by the Arapahoe County Sheriff's Office shows James Holmes shortly after his arrest. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Arapahoe County Sheriff, file)

    FILE - This file photo released on Sept. 20, 2012 by the Arapahoe County Sheriff's Office shows James Holmes shortly after his arrest. Holmes faces trial starting on April 27, 2015, in the mass shooting in an Aurora, Colo., movie theater that left 12 dead and 70 wounded. (AP Photo/Arapahoe County Sheriff, file)  (The Associated Press)

The key to understanding the death penalty trial of James Holmes, the man who killed 12 people and wounded 70 more at a packed Batman movie premiere, will be to learn what was going on inside his mind at the time.

Opening statements start Monday in the long-awaited trial of the 27-year-old, who has pleaded not guilty by reason of insanity. His July 20, 2012, attack in suburban Denver was among the deadliest in American history.

Holmes' lawyers say he was psychotic and could not tell right from wrong. But prosecutors say he carefully planned the shooting for months.

They will ask the final 12 jurors selected from a pool of 9,000 citizens to sentence Holmes to death. If they decide instead on insanity, he will be committed to a state mental hospital.