CENTENNIAL, Colo. >> Half-empty tissue boxes littered the floor of Courtroom 201 after a day in which survivors told stories of heartbreak, revulsion and horror about the night James Holmes shot scores of people inside a packed a suburban Denver movie theater.

Some in the courtroom reached for the colorful boxes to wipe their eyes as more than two dozen victims and first responders — each with their own tragic stories — testified during the first week of Holmes’ trial, describing how a theater full of moviegoers excited to see a new Batman film became a scene of life-altering carnage and terror.

Defense attorneys have urged jurors not to let emotions sway them, but with weeks of harrowing testimony still to come, experts say Holmes’ lawyers will have a difficult time convincing jurors to put sympathy behind them as they decide whether he was legally insane when he killed 12 people and injured 70 others in July 2012.

Judge Carlos A. Samour Jr. has reminded jurors to keep an open mind. But the average person isn’t trained to do that, said Joseph Rice, managing partner of the Jury Research Institute, a California-based trial consulting firm.

“Once you have that visceral gut reaction to a scene or a sympathetic connection with a party, it’s virtually impossible to treat this in an academic way,” he said.

Each witness has offered their own painful vantage point on the attack. Among those jurors heard from last week:

— Caleb Medley, who suffered brain damage and paralysis from a shotgun blast to the face, could only speak in grunts from the witness stand or by pointing to letters of the alphabet on a poster.

— Justin Grizzle, a police officer, told of carrying Medley in the back of his patrol car and begging him not to die as he sped to a hospital.

— Kaylan Bailey, who was 13 when the attack occurred, described calling 911, shrieking that her 6-year-old friend Veronica wasn’t breathing. Prosecutors also played the hair-raising call in court.

— Detective Matthew Ingui showed photos of the bodies wedged between rows of seats or sprawled on the floor amid popcorn, spent ammunition and shoes left behind in the panic to escape. The photos sent one woman darting from the courtroom. Holmes’ mother, Arlene, gripped her husband Robert’s arm and pulled him close. Some in the crowded gallery held each other and wept.

— District Attorney George Brauchler had one gunshot victim, Joshua Nowlan, hold his cane — which he uses after bullets pierced his leg that night — like an assault rifle to show the way he saw Holmes spraying gunfire into the crowd.

Holmes’ attorneys don’t dispute what happened inside the Century 16 movie theater in Aurora, and they don’t deny Holmes was the shooter. They have cross-examined only a few prosecution witnesses. None were victims.

Holmes has pleaded not guilty by reason of insanity to 165 counts of murder and attempted murder, and defense attorneys say his mind was so distorted by schizophrenia that he didn’t know right from wrong. If the jury finds he was insane, he would be committed indefinitely to the state mental hospital.

Prosecutors have described Holmes as calculating and smart and say he believed killing others increased his self-worth. They are asking jurors to convict him of murder and sentence him to death.

They have worked to ingrain in jurors’ minds a powerful image of gore and grief that will be challenging for the defense. Already at their disadvantage are two court-mandated mental evaluations that found him sane, and the emotional case prosecutors are building is another hurdle, experts say.

“The defense certainly has a difficult situation because of all the misery that was caused by, that they admit was caused by, James Holmes,” said Dan Recht, a longtime Denver defense attorney who isn’t involved in the case.

Holmes’ lawyers plan to call an expert witness who will testify that Holmes was insane: Dr. Raquel Gur, head of the neuropsychiatry program at the University of Pennsylvania medical school.

“The jury is going to be confronted with experts saying diametrically opposed things, and they’re going to have to make the decision based on that,” Recht said.

All the defense needs to do is cause reasonable doubt in the jurors’ minds about whether Holmes was sane, Recht said. In Colorado, the burden is on prosecutors to prove that a defendant is sane, rather than the reverse.

The prosecution is far from finished in calling survivors and first responders to testify. More are expected to be called to the stand in the weeks to come.

“These are pure victims who are going to a movie theater, they did not put themselves in harm’s way,” Rice said. “It’s your worst nightmare.”