In imposing sentence, Judge Samour declared "it is the intention of this court that the defendant never set foot in free society again.

[16] Holmes was raised in Oak Hills, a community in Monterey County near Castroville, California, where he attended elementary school.

[30] In Aurora, Holmes lived on Paris Street in a one-bedroom apartment in a building with other students involved in health studies at the University of Colorado.

"[43][44] In 2006, Holmes worked as an intern at the Salk Institute for Biological Studies, where he was assigned to write computer code for an experiment.

Holmes, who was described by his supervisor as stubborn, uncommunicative and socially inept, presented his project to the other interns at the end of the internship, but never completed it.

"[47] Graduating from Westview High School in the Torrey Highlands community of San Diego in 2006,[48][49] Holmes attended the University of California, Riverside (UCR).

[54] According to UCR recommendation letters submitted to the University of Illinois at Urbana–Champaign (UIUC), Holmes graduated in the top 1 percent of his class with a 3.949 GPA.

The UCR letters also described Holmes as "a very effective group leader" and a person who "takes an active role in his education, and brings a great amount of intellectual and emotional maturity into the classroom".

She listed specific concerns, such as his long-standing fantasies about killing as many people as possible, his reluctance to discuss any details about his plans, his refusal to allow them to talk to anyone else and the unclear timeline; she didn't know if he was always that way or if this was a new behavior.

[65] Three days after failing a key oral exam at the university in early June 2012, Holmes dropped out of his studies without further explanation.

[76] Dave Aragón, an actor from the MTV television series Pimp My Ride, stated that Holmes called him twice the month before the shooting took place.

[85][86] On July 2, he placed an order for a Blackhawk Urban Assault Vest, two magazine holders, and a knife at an online retailer.

The owner, Glenn Rotkovich, called him several times throughout the following days to invite him to a mandatory orientation, but could only reach his answering machine.

[91] Immediately prior to the shooting, Holmes reportedly called a crisis hotline for mental health with the hopes that someone would talk him out of committing the massacre at the last minute.

[92] Holmes snuck out of an exit door, propped it open, and returned with weapons and other gear, setting off several gas or smoke canisters.

According to testimonies during the following trial, Holmes was initially "calm and detached" during the arrest, but became interested in watching the aftermath of the shooting after being placed in the back of a police car.

[110] On September 28, court documents released by prosecutors said Holmes’ access to the University of Colorado campus was revoked because he threatened a professor.

[112] Holmes' lawyers filed an emergency motion on November 14 to delay a pre-trial hearing, citing an unspecified condition that left him unable to appear in court: "As a result of developments over the past 24 hours, Mr. Holmes is in a condition that renders him unable to be present in court for tomorrow's hearing."

[114] Holmes returned to court on January 7, 2013, at which 9-1-1 phone call recordings and videos from the cineplex were presented as evidence, information that up until then had not been released.

Holmes's defense team continued to maintain that he was mentally ill.[115] On that same day, it was reported that investigators seized four prescription bottles plus immunization records from his apartment when it was searched in July 2012.

[128] On February 27, 2014, Arapahoe County District Court Judge Carlos Samour set the start of Holmes' trial for October 14.

[129][130] On that date, the trial was again postponed, as Holmes' lawyers asked for another continuance to further prepare their case and review the paperwork of evidence.

The defense opened their argument by admitting the fact that Holmes was the shooter, but said that he was mentally ill with severe schizophrenia and was never in control of his right mind.

Reid and another doctor evaluated Holmes in December 2013, determining him to be legally sane, and said that his mental illness did not prevent him from forming intent and knowing the consequences of his actions.

[40][139] On June 8, a second psychiatrist, Jeffrey Metzner, testified that Holmes was mentally ill but legally sane when he plotted and carried out the shooting, and that he suffered from schizoaffective disorder.

[153] On July 23, the jury ruled that Holmes acted in a cruel manner, was lying in wait, and ambushed his victims during the shooting, which constituted aggravating factors.

[154] On July 27, Holmes's sister testified that her brother became withdrawn from the family after they moved from Salinas to San Diego during his early teenage years.

On July 28, Holmes' father pleaded for his son's life, stating that he is severely mentally ill and did not deserve to die, regardless of his crimes.

[155] On July 30, Holmes' lawyers made a final appeal to the jurors, urging them to consider mental illness in his sentencing, despite their rejection of the insanity defense used in the trial.

[166] The exact reason for the transfer to federal custody is not known for certain; the Washington Post speculated that it was, in part, due to a heightened need for security.