The Aurora massacre revived the perennial US debate over gun control -- an issue re-ignited even more intensely by last month's shooting of 20 young children at a Connecticut elementary school.
The emotionally fraught preliminary hearings opened Monday with police describing harrowing scenes as they responded to the theater where 25-year-old James Holmes is accused of opening fire.
A number of officers choked back tears as they testified about the night, in which 12 people were killed and dozens more injured at the midnight screening of the Batman movie "The Dark Knight Rises," in Aurora, outside Denver.
Officer Justin Grizzle, a former paramedic, said he almost slipped over in a "huge amount of blood" as he entered the back entrance to the Century 16 movie theater.
As ambulances struggled to cope with the scale of the slaughter, Grizzle described how he transported six critically ill victims in four trips to area hospitals.
"I realized later that as I was slowing to make turns, I could hear blood sloshing in the back of my car," Grizzle testified, choking as he remembered the night.
As relatives pulled out their handkerchiefs in court, another first responder recalled finding the youngest victim of the shooting, six-year-old Veronica Moser-Sullivan, with no pulse amid the carnage.
Sergeant Gerald Jonsgaard, one of the first officers on the scene, described finding the child as he entered the theater shortly after midnight on July 20.
"She had been carried down from the top to the front of the theater. I checked for a pulse. She was dead," he said, voice breaking. A colleague said he felt a pulse, but the child was declared dead on arrival in hospital.
Holmes, sporting dark brown hair and a full beard, was led into court in handcuffs at the hearing to decide whether there is enough evidence to put him on a full trial.
Clad in dark red prison scrubs, Holmes -- who had bright orange hair when he first appeared in court shortly after the shooting -- stared straight ahead and talked to no one.
Aurora policeman Jason Oviatt told the court how he at first thought Holmes was another officer when he arrived with dozens of other police in response to 911 emergency calls about the shooting at a screening of the new Batman film.
Holmes had his hands on the top of a white car at the back of the building, and as Oviatt approached, he saw he was not a fellow officer.
"As I got closer the man was just standing there, not moving. The overall picture didn't match a police officer as I got closer," said Oviatt.
Holmes offered no resistance when he was ordered to put his hands up.
"He was completely compliant... He was very relaxed, there weren't normal reactions to anything... He was very detached," Oviatt said, adding: "He seemed to be out of it, and disoriented."
Witnesses said Holmes threw smoke bomb-type devices before opening fire randomly with weapons including an AR-15 military-style rifle, a 12-gauge shotgun and a .40-caliber pistol.
His one-bedroom apartment was later found to be booby-trapped with an array of home-made explosive devices, which police had to disarm before entering.