CENTENNIAL, Colo. -- Katie Medley, nine months pregnant and crouching between the seats of a movie theatre filling with tear gas, gunfire and screams, looked at her husband Caleb's bloody face and told a friend, "He's dead, he's dead."

Prodeo Et Patria was 14 that night, and sitting with his parents somewhere in the middle of the 421 people watching a midnight Batman premiere. He thought the gunfire was a joke until his father ordered him to the floor, where someone kicked off his glasses in the chaos.

His father told him to run and refused to leave his mother, whose arm and foot were shattered by bullets. Hoisting his wife onto his back, they made for an exit together. "That's when I first felt a gunshot hit me," Patria said.

They were the among the first of many prosecution witnesses in the death penalty trial of James Holmes, and their gripping testimony made clear the state's determination to make sure jurors know the carnage Holmes caused inside the suburban Denver theatre on July 20, 2012.

Judge Carlos A. Samour Jr. warned jurors as the trial opened not to let sympathy and emotion influence their judgment. The defence team has conceded that Holmes was the killer, hoping to focus not on the crime itself or its lingering damage, but on what it sees as the only question jurors must resolve: whether Holmes was legally insane at the time.

But on this first long day of testimony, the judge repeatedly turned away defence objections to particularly gruesome and tragic details. Defence attorneys did not question any of the witnesses from the theatre.

Defence attorney Katherine Spengler argued that grisly photos, an emergency services call recording of shrieks and screams, and the words "bloody victim" that a witness wrote on a diagram of the theatre served only to inflame the jury. The judge dismissed her motions, reasoning that the evidence is relevant and fairly depicts a horrific crime.

Prosecutors say they will prove beyond a reasonable doubt that he was sane, therefore guilty, and should be executed. Holmes has pleaded not guilty by reason of insanity; his defence hopes the jury will have him indefinitely committed to a mental institution.

Tuesday was Day One of testimony in a trial expected to last four months or more. If the prosecution keeps this up into August, the cumulative weight of the victims' suffering could make the defence job even more difficult.

In opening statements, the defence sought to focus instead on what was going on inside Holmes' mind, which they say was so addled by schizophrenia and psychosis that his sense of right and wrong was distorted, and he lost any control over his actions. They won't call their own witnesses or begin making the case for insanity until after the prosecution rests, many weeks from now.

Defence lawyers said Holmes was a "good kid" who sensed something wrong with his mind, even at a young age. Studying neuroscience at the University of Colorado was his attempt to fix his thoughts; Instead, "psychosis bloomed" when he failed in the doctoral program, and delusions then commanded him to kill, they said.