By Keith Coffman CENTENNIAL, Colo., May 5 (Reuters) – Colorado movie theater gunman James Holmes’ apartment was rigged with improvised explosive devices, jars of napalm and fire-accelerating chemical powder sprinkled on the floor, an FBI expert told jurors at his trial on Tuesday. Prosecutors say Holmes, a 27-year-old former neuroscience graduate student, planned to divert first responders by destroying his home in the Denver suburb of Aurora while he opened fire on a packed midnight premiere of the Batman film “The Dark Knight Rises.” Holmes has pleaded not guilty by reason of insanity to multiple counts of murder and attempted murder for killing 12 people and wounding 70 in the July 2012 rampage. FBI bomb technician Special Agent Garrett Gumbinner, who interviewed the defendant soon after his arrest, showed the jury photos from Holmes’ apartment near the theater, some taken with a remote-controlled bomb robot. He said the images showed a booby trap made from fishing line connecting the front door to a thermos of glycerin, sitting above a frying pan full of potassium permanganate, an explosive combination. Prosecutor Rich Orman asked what would have happened if the tripwire had been triggered. “The … reaction would have caused sparks and flames which would have hit the carpet which was saturated with gas and oil, which would in turn have made the whole apartment explode, killing or maiming whoever was inside at the time,” Gumbinner replied. Magnesium powder was sprinkled on the carpet, Gumbinner said. When doused with water by firefighters, it would have strengthened the flames and given off a noxious gas, making it more dangerous for emergency crews. Jars of napalm and bottles of gasoline had been placed on furniture. Jurors have also been played video and audio of Holmes being interviewed by the FBI agent and Aurora police detectives. Mostly giving slow, one-word answers, Holmes is heard asking in the video whether any children were hurt in the attack and in the audio recording apparently describing the explosive devices in his apartment. But that audio was particularly poor, and the defense objected to a transcript made by the FBI that was given to jurors, arguing much of it was inaudible. Arapahoe County District Court Judge Carlos Samour overruled the objection but cautioned the jury of 19 women and five men that the transcript was only a guide. Prosecutors say Holmes carried out the massacre because he had lost his career, girlfriend and purpose in life. Holmes’ public defenders say he suffers from schizophrenia and heard voices in his head telling him to kill. The trial is expected to last four or five months. (Reporting by Keith Coffman; Editing by Daniel Wallis and Cynthia Osterman) (([email protected]; 303-335-5080; Reuters Messaging: [email protected])) Keywords: USA SHOOTING/DENVER