A courtroom sketch of James Holmes, center left, with defense attorney Daniel King in court at the Arapahoe County Justice Center on Monday. (Jeff Kandyba/AP)

Nearly three years after a gunman inside a Colorado movie theater opened fire, killing 12 people and wounding dozens more, an unusual trial is taking place in a courtroom about half an hour away from the theater.

James Holmes, who is facing more than 140 charges related to the shooting and its aftermath, has pleaded not guilty due to insanity. His attorneys sought to move the trial, because of the publicity the case has received, but Carlos A. Samour Jr., the district judge, rejected the request. Samour wrote in an order last week that because the shooting became national news, “transferring a highly publicized case like this one from one large county to another within the state of Colorado would be as useful as installing a screen door on a submarine.”

Still, when these kinds of mass shootings tear through schools or shopping malls, they are often followed by public mourning, lingering questions and calls for change. They are not typically followed by a trial that offers a judge and jury an opportunity to weigh the case of a gunman after his name and actions dominate the headlines.

In large part, this is due to the nature of these types of shootings and the way they often end. An FBI study examining 160 “active shooter” incidents in the United States over more than a decade found that most of these shootings ended when the person stopped firing. These incidents usually ended because the person committed suicide, which happened in nearly half of these cases. More than half of these shootings ended with the shooter dead at his own hands or after being killed by police. Cases like this trial or that of Nidal Hasan, the Army psychiatrist sentenced to death for killing 13 people at the Fort Hood military installation in Texas, are less common.

As a result, the long-delayed trial could offer a look at the questions often raised by a mass shooting — what else could have been done? Could it have been prevented? — and try to answer them through a procession of statements and arguments, evidence and testimony, rather than in the cold, diagnostic language of an official report issued months or years later.

But for survivors of the shooting and the friends and family of the people who were killed, it offers something else, something more painful. Marcus Weaver, a survivor of the shooting, recently wrote for the magazine 5280 that the past “threatens to grip me ever tighter as the trial date grows closer.” The trial extends an agony that may never end. It also offers some hint at resolution, the justice system’s attempt at making sense out of the incomprehensible.

Jury selection in the case began in January, following a series of delays that repeatedly pushed back the beginning of the trial. After prosecutors criticized the first evaluation of Holmes’s sanity, a second evaluation was ordered, which then took longer than mental health professionals expected. Ultimately, a pool of 24 people — a dozen jurors and another 12 alternates — was selected earlier this month. Its ranks include a survivor of the Columbine High School shooting in 1999.

These jurors weighing Holmes’s sanity are also going to have to figure out whether he should be put to death for his actions. Prosecutors are seeking the death penalty in this case. (Colorado has only executed one person over the last four decades.) It is unclear how the insanity defense will play out across the trial, as a highly-cited study said that this argument is rarely used and successful only about a quarter of the time.

Holmes’s mental state is also cited by his family as the reason he should be allowed to live. In a letter late last year, his parents pleaded for Holmes’s life, instead asking that he be condemned to life imprisonment. “We do not know how many victims of the theater shooting would like to see our son killed,” Robert and Arlene Holmes wrote. “But we are aware of people’s sentiments. We have read postings on the Internet that have likened him to a monster. He is not a monster. He is a human being gripped by a severe mental illness.”

The trial could last until the end of the summer or into the fall.