A verdict saying a Colorado movie theater could not have safeguarded against a shooting that left 12 people dead likely prevented a major shift in how people go to the movies by keeping the onus on the killer, rather than the public venue he chose to attack.

Six jurors concluded Thursday that Cinemark was not liable for the 2012 rampage, quickly rejecting victims' arguments that, in an age of mass shootings, the theater should have foreseen the possibility of violence at a crowded midnight premiere of a Batman film.

Several survivors and families of the dead sued the nation's third-largest theater chain, saying the suburban Denver theater should have had armed guards at the summer blockbuster. There also was no silent alarm that would have sounded when James Holmes slipped into an auditorium and started shooting.

The civil case was watched closely by theater security consultants, some of whom predicted that a verdict against Cinemark would mean sweeping and costly changes to the way theaters protect customers. Some experts said a loss could have forced theater companies across the country to use metal detectors or hire more security, hiking up ticket prices to offset the cost.

Cinemark argued that no security measures could have stopped the armor-clad Holmes. After months of meticulous planning, he threw gas canisters into the crowd of more than 400 and then opened fire with a shotgun, assault rifle and semi-automatic pistol.

"Cinemark endured a tremendous tragedy as did the victims of the case and the entire Aurora community ... at the hands of a madman, James Holmes," Cinemark attorney Kevin Taylor told reporters. "Mr. Holmes was clearly unpredictable, unforeseeable, unpreventable and unstoppable. ... The only thing that matches the unforeseeability of this case is the tragedy of it."

Marc Bern, an attorney for the victims, said he would ask a judge to set aside the verdict while the victims appeal.

"These victims of this tragedy have been dealt another blow," Bern said. "Cinemark failed to do a number of things that should have been done. ... They're going to have to wait some time now before they get justice."

Holmes was sentenced to life in prison last year after a different group of jurors failed to agree unanimously that he deserved the death penalty.

Taylor told jurors that it the first mass shooting at a theater "in the history of American cinema," arguing such shootings are still so rare that management could not have anticipated one at a theater with no history of serious violence.

Other Cinemark theaters had guards in place for the opening of "The Dark Knight Rises," which was expected to draw more than 1,000 people. Taylor argued they were not needed for the Thursday premiere in suburban Aurora, though the theater staffed guards on Friday, Saturday and Sunday.

Jurors and victims left the courthouse without speaking to reporters.

It's unclear whether the verdict could affect several other civil trials stemming from the shooting. Another case against Cinemark involving at least 40 other victims is set to open in July in federal court.

Victims also are suing Holmes' University of Colorado psychiatrist, arguing she and other university officials should have done more to stop the attack after Holmes confessed his homicidal thoughts.