The jury selection for the trial of James Holmes, the man accused of open firing at a Colorado movie theater – killing 12 and injuring more than 50 others – is underway in Arapahoe County.

James Holmes Jury Selection

Court officials summoned an unprecedented jury pool of 9,000 people. However, the number – the largest in U.S. history – dwindled down to 7,000 due to delivery issues and some people getting excused.

“I’ve never heard of that many people,” CNN senior legal analyst Jeffrey Toobin said. “It just shows how these high-profile cases impose such tremendous costs on the community.”

On Tuesday, Judge Carlos Samour will likely only see 188 of the potential jurors, reported NBC News.  “This will require great effort on your part,” the judge told each of the groups of jurors that came before him, referring to the necessity that they avoid any media concerning the case.

Holmes, 27, has pleaded not guilty by reason of insanity for the charges stemming from the July 2012 massacre inside a showing of The Dark Knight.

“The public overestimates the frequency and success of the insanity plea, and misunderstands the consequences. So this hostility toward the defendant’s insanity plea will be a major challenge during [the juror questioning],” according to law professor Valerie Hans.

Once the jury is selected, the trial will commence and likely go on for roughly four months. If found guilty, Holmes could face the death penalty in a sentencing trial.