(CNN) -- Those deciding accused Colorado movie theater shooter James Holmes' fate should expect the whole process to take eight months, a judge ruled Wednesday, suggesting -- while few question who is behind the massacre -- that other factors might prolong the case.
District Court Judge Carlos Samour Jr. detailed his estimate in an order Wednesday pertaining to the questionnaire prospective jurors will have to fill out.
Agreeing with the prosecution that it's better to overestimate than underestimate how long everything will take, Samour said jurors will be told jury selection could go on for two to three months. The actual trial will last four to five months more, he said.
Other parts of the judge's order allude to what may be the biggest complicating factor in the trial: mental health, including the prospect of a person pleading not guilty by reason of insanity, as Holmes has done.
At the defense's request, for example, one grouping of questions will fall under a "mental health" or "mental illness" subheading, ruled Samour. One question jurors will be asked: "Do you have strong opinions -- good or bad -- about mental health providers?"
The burden is on the prosecution to prove that Holmes was sane at the time of the shootings.
Jury selection in the case is expected to begin February 3, 2014, according to Colorado state courts spokesman Rob McCallum.
About 400 moviegoers in Aurora, Colorado, were settling into a July 2012 midnight showing of the latest Batman installment, "The Dark Knight Rises," when a man dressed head-to-toe in protective gear enters.
Propping open the door, he exploded tear gas canisters in the theater, then began shooting, according to witnesses. Police say he used several weapons, including an AR-15 rifle, before fleeing the theater.
It's there where the shooter was apprehended, identifying himself to police as "The Joker," one of Batman's archenemies.
Holmes faces 166 charges in the rampage, which left 12 people died and another 70 wounded.
"He didn't care who he killed," prosecutor Karen Pearson said last January, saying Holmes chose his venue carefully to cage his victims. "He intended to kill them all."
Holmes was a neuroscience doctoral student at the University of Colorado's Anschutz Medical Campus until the month before the attack; prosecutors have argued that he began plotting his attack while still enrolled.
The defense, meanwhile, appears to be focused not so much on what Holmes allegedly did that night but his mental state then and earlier.
A psychiatrist who treated him had warned campus police at the University of Colorado how dangerous he was, prompting them to deactivate his college ID to prevent him passing through any locked doors, according to court documents.
CNN's Karan Olson contributed to this report.