Any new details to emerge this week — including Holmes' mental state — will come amid the discussion over an array of proposals, including tougher gun laws, better psychiatric care and the arming of teachers.
The hearing is the first extensive public disclosure of the evidence against Holmes. Other information has come out, including details about how he legally bought his guns in person and purchased thousands of bullets and body armor online as well as a notebook that he sent to a psychiatrist he had seen.
A district judge forbade attorneys and investigators from discussing the case publicly, and many court documents have been under seal.
It took this long to get to the preliminary hearing because lawyers have been debating what physical evidence should be made available to one side or the other, whether the psychiatrist who met with Holmes is barred from testifying by doctor-patient privilege and who was responsible for media leaks.
It wasn't immediately clear whether the doctor would testify this week.
On Monday, prosecutors called on the first responders to testify about the shooting at the midnight showing of the latest Batman movie, "The Dark Knight Rises," in Aurora. Holmes had bought his ticket almost two weeks in advance. Investigators say Holmes, wearing body armor, tossed two gas canisters into the packed theater and then opened fire.
When officers arrived, they saw people running out of the theater and trying to drive away. Others walked. Some of the wounded tried to crawl out.
Officers found Holmes standing next to his car. At first, Officer Jason Oviatt said, he thought Holmes was a policeman because of how he was dressed but then realized he was just standing there and not rushing toward the theater.
Oviatt pointed his gun at him, handcuffed him and searched him. He said he found two knives and a semi-automatic handgun on top of Holmes' car. An ammunition clip fell out of his pocket and Oviatt found another on the ground. He said Holmes was dripping in sweat and his pupils were wide open.