US

Colo. theater shooting case enters crucial new phase as Holmes seeks to enter insanity plea

FILE - In this March 12, 2013 file photo, James Holmes, left, and defense attorney Tamara Brady appear in district court in Centennial, Colo. for his arraignment. Lawyers for Holmes, the man accused of killing 12 people and injuring 70 in a Colorado movie theater, said Tuesday May 7, 2013 he wants to change his plea to not guilty by reason of insanity. (AP Photo/The Denver Post, RJ Sangosti, Pool, File)

FILE - In this March 12, 2013 file photo, James Holmes, left, and defense attorney Tamara Brady appear in district court in Centennial, Colo. for his arraignment. Lawyers for Holmes, the man accused of killing 12 people and injuring 70 in a Colorado movie theater, said Tuesday May 7, 2013 he wants to change his plea to not guilty by reason of insanity. (AP Photo/The Denver Post, RJ Sangosti, Pool, File)  (The Associated Press)

James Holmes is asking a judge to allow him to change his plea to not guilty by reason of insanity in the deadly Colorado theater shootings.

Holmes will seek the new plea at a hearing Monday. He faces murder and attempted murder charges in the July 20 attack, which killed 12 and injured 70.

No motive has emerged, but Holmes' attorneys have repeatedly said their client is mentally ill.

Prosecutors are seeking the death penalty.

The insanity plea carries risks for both sides. Holmes must submit to a mental evaluation by state doctors, and their findings could be used against him by prosecutors.

The plea also makes it harder for prosecutors to get a conviction. They must convince jurors that Holmes was sane at the time of the shootings.