Colorado theater shooter James Holmes went from happy boy to mass killer

FILE - In this July 29, 2015 file image made from Colorado Judicial Department video, a family photo is displayed on the screen showing James Holmes when he was a toddler, as James Holmes' mother Arlene, top right, gives testimony during the sentencing phase of the Colorado theater shooting trial in Centennial, Colo. James Holmes sits in court at far left. A fuller portrait of the Colorado movie theater shooter has emerged during Holmes' death penalty trial. Testimony given by Holmes' parents revealed a family laid bare by the tragic consequences of a son's incomprehensible descent from a well–behaved child with a quirky sense of humor into a killer capable of gunning down defenseless strangers. (Colorado Judicial Department via AP, Pool, File) (The Associated Press)

FILE - In this July 28, 2015, file image, made from Colorado Judicial Department video, defense attorney Tamara Brady, left, questions Robert Holmes, top right, the father of James Holmes, background left in white shirt, during the sentencing phase of the Colorado theater shooting trial in Centennial, Colo. A fuller portrait of the Colorado movie theater shooter has emerged during Holmes' death penalty trial. Testimony given by Holmes' parents revealed a family laid bare by the tragic consequences of a son's incomprehensible descent from a well–behaved child with a quirky sense of humor into a killer capable of gunning down defenseless strangers. (Colorado Judicial Department via AP, Pool, File) (The Associated Press)

CENTENNIAL, Colo. – A fuller portrait of Colorado movie theater shooter James Holmes has emerged during his death penalty trial.

But 12 weeks of testimony about his unremarkable childhood and college years have made it even more difficult to understand his decline into a killer capable of shooting strangers in a crowded auditorium.

Jurors rejected Holmes' insanity plea and convicted him of killing 12 people and injuring 70 more in the July 2012 attack. Now they must consider his early years as they decide whether to sentence him to death or life in prison without the possibility of parole.

Family, friends and former neighbors have all testified about his seemingly happy, average life before the shootings. His defense team says he was mentally ill and hopes jurors will show mercy and spare him from execution.