Updated

The first wave of a 9,000-member jury pool - the largest in U.S. history - appeared in a Colorado courtroom Tuesday as the trial of James Holmes, who is accused of murdering 12 and injuring seven in a 2012 attack at an Aurora, Colo., movie theater, got underway more than two-and-a-half years after the attack that stunned the nation.

Holmes, who wore a blue blazer, striped shirt and khaki slacks and appeared better groomed than in appearances shortly after the attack, sat attentively as the first batch of prospective jurors went through the screening process. An historic number of juror summonses - some 9,000 - were sent for the trial of James Eagan Holmes. In court filings, Judge Carlos A. Samour Jr. has indicated he set such a large number for the pool of potential jurors because it is a high profile, death penalty case.

By comparison, 3,000 were recently summoned for selection in the trial of accused Boston Marathon bomber Dzhokar Tsarnaev. The 1994 O.J. Simpson case brought in 1,000.

Samour addressed the first group of 250 jurors, who then were to spend two to three hours answering more than 70 written questions that have not been made public.

After Tuesday, groups of 250 will follow the same routine every morning and afternoon for a month. Based partly on the questionnaires, many will not be asked back for individual jury selection, which is scheduled to begin February 17.

Individual Voir Dire will continue until a whittled down group of 120 to 150 is left. From them, the final jury of 12 and 12 alternates will be seated.

Jury consultant Carolyn Robbins Manley, who is not involved in the case, says lawyers will need to explore the amount of pretrial publicity to which people have been exposed. "You don't have to live in a cave, you can obviously know about the incident,” she said. "The question is, specifically, whether you can be fair, can you start out not having been persuaded by what you've heard."

Both jury selection and the trial are taking place in Arapahoe County, the same county where the shooting on July 20, 2012 left 12 dead and 70 injured. A request by the defense for a change of venue was denied.

Eventual jurors have to be what is known as “death qualified,” meaning they are willing to impose the death penalty if warranted. "It's not really selection, it's de-selection, so the goal is for each side to root out biases," said Robbins Manley.

Holmes, charged with 166 counts of murder, attempted murder and other charges, has pleaded not guilty by reason of insanity.  Under Colorado law, the burden is on the prosecution to prove Holmes knew right from wrong at the time.

During jury selection, Robbins Manley said the defense will want to explore prospective jurors' feelings about the insanity defense, any experiences they have had with psychiatry and whether they have any family members that may be mentally ill.

She added prosecutors will look to find, "People who just might think the insanity plea is fluff and it shouldn't exist." They will also look for those who are supportive of the judicial system, have had positive experiences with the law, and who are respectful of law enforcement.

In December, just days after summonses were mailed, Holmes' parents, Robert and Arlene Holmes, released an open letter to the media. It read in part, "We realize treatment in an institution would be best for our son. We love our son, we have always loved him and we do not want him to be executed. We also decry the need for a trial. A lengthy trial requires everyone to relive those horrible moments in time, causing additional trauma."

"The timing of the parents' statement in this advocacy for the defendant, might have backfired. They may have aggravated more people than actually got them on their side," Robbins Manley said.

Defense attorney Dan Recht, who is not involved in the case, said, "...were they thinking that jurors would read it? Probably. And was there coincidence in the timing?  No, probably they thought this is a good time to release this statement... that can't be held against the defense team. It wasn't issued by the defense team. It was issued by these grieving parents."

Meanwhile, some victims are concerned about the public attention being paid to Holmes. Tom and Caren Teves, parents of Alex Teves, one of the 12 who died in the theater, released a statement to media that read in part, "Beyond the initial identification of the shooter, we ask that you refer to the individual who opened fire in the theater on July 20th as 'the shooter' or 'the defendant'  throughout your story."

On a website dedicated to the memory of their son, they are promoting their suggested media guidelines and protocol.This includes asking the media to avoid using photos of Holmes because, "This kind of infamy is one of the motivating factors for copycat killers in this nation."

Samour has scheduled opening arguments for the beginning of June, but has said during hearings he could move it up to the beginning of May if jury selection goes faster than he expects.