DENVER >> If James Holmes is found not guilty by reason of insanity in the Colorado theater massacre, he would be committed indefinitely to the state mental hospital and could — in theory, at least — be released someday.

But psychiatrists and attorneys say that’s highly unlikely, given the enormity of the shootings and the notoriety they have generated.

“He doesn’t stand a snowball’s chance in hell of ever walking off the grounds of the Colorado state hospital,” said Dr. Steven Pitt, a forensic psychiatrist based in Scottsdale, Arizona, who works on criminal cases but is not involved in the Holmes case.

Jury selection starts Tuesday for Holmes, who is charged with multiple counts of murder and attempted murder in the July 20, 2012, shootings at a Denver-area movie theater. Twelve people were killed and 70 were injured. Prosecutors are seeking the death penalty.

Holmes pleaded not guilty by reason of insanity. His attorneys have acknowledged he was the gunman but say he is mentally ill and was gripped by a psychotic episode when he opened fire on a theater in the Denver suburb of Aurora, where more than 400 people were watching a midnight showing of “The Dark Knight Rises.”

Colorado law defines insanity as the inability to know right from wrong because of a mental illness or defect. The jury will make that determination based on evidence presented at the trial, including two court-ordered sanity evaluations at the Colorado Mental Health Institute at Pueblo.

The law sets no minimum time that people must remain in the state hospital after being found not guilty by reason of insanity, except to say they can’t ask for a release hearing in the first 180 days.

Patients who show progress can be granted a measure of independence, ranging from supervised movement around the hospital grounds through off-campus visits to unconditional release.

To qualify for unconditional release, Holmes would have to convince the hospital and the courts that he is no longer a threat to the public for the reasonably foreseeable future — the standard for release set by Colorado law.

That would be a tough case for Holmes to make, said Karen Steinhauser, a former Denver prosecutor who is now a defense attorney.

State records show the vast majority of people granted off-hospital-grounds privileges after being found not guilty of murder because of insanity were charged with killing someone they knew, usually a family member. Although the available court records are often sketchy, in some cases the insanity defendants believed the victim was somehow tormenting them.

Holmes, by contrast, is charged with a brutal attack on complete strangers.

“The issue is going to be, how do we know that this person no longer has that type of mental disorder that could cause him to go to a different place, to a different community, to a different area and do the same thing?” said Steinhauser, who isn’t involved in the Holmes case.

It would be nearly impossible for Holmes to convince a judge he was no longer a danger to himself or others, she said.

Pitt, the forensic psychiatrist, said it is theoretically possible that treatment by psychiatrists could put Holmes’ mental illness into remission and render him no longer a danger.

“Theoretically, is that possible? Absolutely,” he said.

“From a social policy perspective, given the enormity and the gravity of the offenses … there will be such an uproar that I just can’t realistically ever see that happening in the foreseeable future,” Pitt said.

John Hinckley, who was found not guilty by reason of insanity in the 1981 shootings of President Ronald Reagan and three others, has been committed to a psychiatric hospital for 32 years. Hospital officials have said his mental illness has been in remission for decades, and he spends more than half of each month at his mother’s home.

Dr. Patrick Fox, a deputy director of the Office of Behavioral Health in the Colorado Department of Human Services, which oversees the state mental hospital, acknowledged that social and political factors as well as the notoriety of a crime can sometimes play a significant role in decisions about an insanity defendant.

“The decision to release an insanity acquittee is a partly clinical process. It’s partly a socio-political process,” Fox said. He declined to discuss Holmes’ case in particular, citing privacy issues.

The district attorney’s office that handled the original case can argue against such privileges before the judge decides, and prosecutors would certainly argue strongly against any freedoms for Holmes, Pitt said.

“For generations to come, he will see objection after objection after objection to this man receiving anything that people sense is remotely close to a sense of freedom,” Pitt said.