A few family members of victims sat in the front rows of the second-floor courthouse, some of them staring hard at Mr. Holmes as defense lawyers and prosecutors discussed whether there should be limits on what information was conveyed to the news media and said they would grant the defense access to Mr. Holmes’s apartment and the suburban theater where the shooting occurred.

It was all over in less than 15 minutes, and Mr. Holmes was led back to jail, where he is being held away from other inmates. He will continue to be held without bond.

Outside the courthouse, the Arapahoe County district attorney, Carol Chambers, said Mr. Holmes could face a multitude of charges. Not only were 12 people killed and 58 injured, but the police also say that Mr. Holmes lay explosive booby traps in his Aurora apartment that appeared designed to kill police officers or any first responders.

Ms. Chambers said investigators were still poring over “an enormous amount of evidence.”

“We would never presume that it would be slam-dunk,” she said. “We will work very hard on this case to prosecute it, just like we would any other case.”