The judge in the Aurora theater shooting case is prepared to summon the largest jury pool ever called in Colorado if the case goes to trial.

The 5,000 summonses that Judge Carlos Samour said this week he intends to send out to prospective jurors would dwarf other jury pools summoned in Colorado and would be at least among the largest called in U.S. history, according to a national expert on jury selection.

People on the jury rolls in Arapahoe County, where the trial is scheduled to start in February, would have a roughly 1-in-90 chance of being summoned for the trial.

“By anybody’s standard, this is a very large number,” said Jeffrey T. Frederick, the director of the Jury Research Services Division of the National Legal Research Group, a trial consulting firm.

Frederick said he has heard of jury pools for other cases numbering in the thousands, but he couldn’t recall any larger than the one Samour has proposed.

The reason for the pool’s enormity is that the theater shooting case is a confluence of things that make it difficult to seat a jury.

The attack last summer on the Century Aurora 16 movie theater killed 12 people, wounded 58 more by gunfire, caused hundreds inside the theater to scramble for their lives and rippled across tens of thousands of lives in the community. It also generated massive amounts of international news coverage.

Frederick said potential jurors won’t be dismissed simply for knowing about the case, but they must be able to be unbiased — something made harder by the amount of attention the case has received.

“The defendant is presumed innocent,” Frederick said. “So people who cannot hold up that standard theoretically cannot be allowed to sit.”

There are also other challenges to seating a jury. Prosecutors are seeking the death penalty in the case, and suspect James Holmes has pleaded not guilty by reason of insanity to the charges. Jurors selected for the trial, then, need to be capable at the start of both finding Holmes insane or sentencing him to death.

And Frederick said the length of the trial — it is scheduled to last four months, but defense attorneys have said it could take longer — means jurors also must be able to commit that much time. On top of that, Holmes’ lawyers have moved for the jury to be sequestered during the trial.

No state court case in Colorado has ever seen such a large jury pool summoned, said Robert McCallum, a spokesman for the Colorado Judicial Branch. The trials of Robert Ray and Sir Mario Owens, both death-penalty cases, had jury pools of 975 and 900, respectively, McCallum said.

Officials in Eagle County planned to summon a jury pool of up to 1,500 had the sexual assault trial of basketball star Kobe Bryant gone forward, according to media reports.

Nationally, the proposed theater shooting jury pool dwarfs other high-profile cases. The trial in Florida of George Zimmerman, underway now, started with a jury pool of 500. Former Penn State football coach Jerry Sandusky began with a jury pool of 600.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold