It appears that a woman accused of intentionally driving her car into a college homecoming parade, killing four people and injuring several more, is considering pleading not guilty by reason of insanity. For now, the woman has pleaded not guilty to four counts of second-degree murder and more than 40 counts of assault and battery.

The Colorado Springs Gazette reports that the charges stem from an incident in Oklahoma last October. Oklahoma State University was holding its homecoming parade when the defendant’s car went around a barricade and struck spectators.

According to her father, the defendant, 25, has struggled with mental illness and underwent inpatient mental health treatment several years ago. The nature of her mental health condition is not clear, but her attorney believes she is still affected by her illness. He said that her face went blank went told that people had died in the crash, and that she seemed unaware that she was in jail.

However, the judge presiding over the case ruled in December that the defendant was mentally competent to stand trial. The defense attorney is still seeking information from the prosecution, and the judge has declined to set a trial date, so it may be too soon to tell if the defendant will invoke an insanity defense.

There is still so much we don’t know about mental illness. But the law has recognized for centuries that illness can rob us of control over our actions. An insanity defense is fairly rare in Colorado, but there are other strategies that people charged with a felony may be able to use to obtain a not guilty verdict.