Doctor says James Holmes' IQ dropped while in custody

CENTENNIAL, Colo. -- Colorado theater shooter James Holmes' IQ score dropped dramatically over two years he was in jail, possibly because of mental illness.

Dr. Robert Hanlon testified Thursday that Holmes had an above average IQ of 123 when he first examined him in April 2013, nearly a year after he killed 12 people and wounded 70 during a packed movie premiere. But that number fell to 116 by the time Hanlon examined Holmes again in January 2015.

Hanlon says the drop could be caused by schizophrenia or a similar disorder. Hanlon testified as defense attorneys try to convince jurors that Holmes was legally insane when he carried out the attack. But Hanlon's examinations of Holmes did not test for sanity.

Other witnesses have described Holmes' strange behavior in the days and months after the shooting.