FILE - In this April 2015 file pool image taken from Colorado Judicial Department video, Colorado theater shooter James Holmes, far left, sits at the defense table at the opening of his trial in Centennial, Colo. Colorado Judicial Department via AP, Pool, File

Centennial, Colorado - Jurors will hear closing arguments on Tuesday in the trial of Colorado movie massacre gunman James Holmes, as they prepare to decide whether he was legally insane or a calculating mass murderer when he killed a dozen people.

Prosecutors and the defense have been allotted two hours each to present their case by Arapahoe County District Court Judge Carlos Samour, after testimony in the almost three-month-long capital trial ended last week.

It is the last time attorneys will address the jury before the panel begins deliberating the fate of the 27-year-old California native on Wednesday.

Holmes, who has pleaded not guilty by reason of insanity, faces 165 counts of first-degree murder, attempted murder and explosive charges stemming from the July 20, 2012 rampage during a midnight screening of a Batman movie in the Denver suburb of Aurora.

When the shooting stopped, 12 moviegoers lay dead and 70 were either wounded by gunfire or injured fleeing the theater. Prosecutors will seek the death penalty for Holmes if he is convicted.

Prosecutors called more than 200 witnesses, interspersing testimony from wounded victims with others who detailed his purchases of weapons, body armor, and the bomb-making materials he used to booby-trap his apartment.

They also called two court-appointed psychiatrists who testified that while severely mentally ill, the onetime neuroscience graduate student was sane when he plotted and carried out the massacre.

The prosecution has said so many victims and their relatives want to attend Tuesday's closing arguments, they will cycle them in and out of the courtroom in groups.

The defense centered on two hired psychiatrists who both concluded Holmes is delusional and schizophrenic, that he heard voices commanding him to kill to enhance his “self worth,” and cannot be held legally accountable.

Prosecutors will address jurors first, and will get the last word with a shorter rebuttal argument after the defense makes its case.

Former Colorado prosecutor Bob Grant, who prosecuted the only death-row inmate executed in the state in 48 years, said the prosecution will remind jurors of Holmes' meticulous planning and the carnage he wrought.

“The district attorney will argue although the defendant is mentally ill, he is not insane under the law, and society deserves its pound of flesh from him,” Grant said.

Holmes has sat impassively through 11 weeks of testimony, occasionally turning to watch videos on a courtroom television. He has rarely interacted with his lawyers or acknowledged his parents, who have been in court for most of the trial.

Defense lawyers have said that if he appears aloof and detached, it is because of the anti-psychotic drugs he takes to control his schizophrenic symptoms.

Looking markedly different from his first court appearance days after the rampage, when he was wide-eyed with dyed red hair, Holmes now wears glasses and his hair has returned to its natural brown. He has put on 30 pounds (14 kg) since his arrest, partly due to the medications, the trial has heard.

Longtime Colorado criminal defense lawyer Mark Johnson said the defense's closing will likely focus on Holmes' psychosis, which its experts testified did not emerge suddenly.

“It could be argued that despite his well thought-out preparation, someone who would go to such lengths with no lucid motive is insane,” Johnson said.

Reuters