Lawyers to argue over fate of Colorado movie gunman Holmes

After hearing 40-minute closing arguments, the panel will deliberate.

Governor Bobby Jindal spoke to the media in front of Johnston Street Java near the Grand Theatre on 23 July 2015 in Lafayette, Louisiana. Picture: AF

CENTENNIAL, COLO - Lawyers for both sides in Colorado's movie massacre trial are due to make closing arguments on Thursday in the penalty phase, then jurors will decide if mitigating factors such as mental illness outweigh aggravating ones that could justify the death penalty.

The jury of nine women and three men has already found the 27-year-old former neuroscience graduate student guilty on all 165 counts for killing 12 people and wounding 70 at a midnight screening of a Batman film at a Denver area cinema.

After hearing 40-minute closing arguments, the panel will deliberate.

If jurors vote unanimously that mitigating factors outweigh aggravating ones, Holmes will get an automatic life sentence with no chance of parole for the July 20, 2012 mass shooting.

If they do not, the jurors will hear victim impact testimony before ultimately deliberating again on whether Holmes should be put to death by lethal injection.

If the jury does not reach a verdict on mitigation before the end of Thursday, deliberations would resume on Monday after a day off on Friday.

During the trial's penalty phase, the jurors have found the prosecution proved aggravating factors which it argued made Holmes' crimes especially depraved, including that the attack was launched "while lying in wait or from ambush."

The panel then heard mitigating witnesses called by the convicted killer's court-appointed attorneys, who described Holmes as a quiet, kind kid who was never in trouble growing up, and who no one thought would go on to massacre a dozen people.

Last, they heard testimony from his younger sister, his statistician father Bob, and his mother, a nurse, Arlene. They all said they still loved him, and blamed severe mental illness for what he did.

"Schizophrenia chose him. He didn't choose it," his mother said.