DENVER (Reuters) - Colorado movie massacre gunman James Holmes researched hallucinations and mental illness in the weeks ahead of the rampage that killed 12 people, as well as bomb-making and terrorism manuals, jurors at his murder trial heard on Wednesday.
Details of the online searches came from police forensic investigator Gordon Madonna, who described for jurors what he found when he scoured the shooter's computers and iPhone following the July 20, 2012 rampage.
Holmes could face the death penalty if he is convicted on multiple charges of murder and attempted murder for opening fire inside a suburban Denver multiplex during a midnight screening of the Batman film The Dark Knight Rises, also wounding 70 people.
The 27-year-old former neuroscience graduate student has pleaded not guilty by reason of insanity.
His public defenders, who called Mr Madonna to testify, said the search results showed Holmes took to the Internet to try to cure himself of severe psychosis, delusions, and voices in his head commanding him to kill.
A defense psychiatrist had earlier testified that the California native chose the field of neuroscience in the hope of fixing what Holmes called in a journal his "broken mind".
Under cross examination by a prosecutor, Mr Madonna said the defendant also ran searches on topics including the Century 16 cinema where the massacre took place, explosives fusing, target shooting, weapons and military tactics.
Prosecutors say his web history proves Holmes methodically planned the rampage, and that he aimed to kill all 400 people inside the theatre, failing partly because his semi-automatic rifle jammed.
Under Colorado's insanity defense statute, they have the burden of proving he was sane at the time of the crime.
Two court-appointed psychiatrists have testified that, while Holmes is seriously mentally ill, he was sane when he planned and carried out the attack.
The defense also called to testify on Wednesday a neuropsychologist who performed a battery of tests on the defendant as part of a court-ordered sanity examination.
Dr Rose Marie Manguso said the onetime undergraduate honours student has an IQ of 123, placing him in the "superior intellect" category.
The defence also played video of Holmes in a police interrogation room after the massacre, as a police officer tapes paper bags onto his hands to preserve gunshot residue.
One officer asks Holmes if he knows what the bags are for.
"Popcorn," he responds.
"Could be used for popcorn," replies the officer. "But not right now."