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.