CENTENNIAL, Colorado — Defense lawyers in Colorado’s movie massacre trial opened their case Thursday, calling a psychiatrist as they seek to prove gunman James Holmes was insane and not in control of his actions when he plotted and carried out the 2012 rampage.

Holmes, a 27-year-old former neuroscience graduate student, opened fire inside a packed midnight premiere of a Batman film at a Denver-area multiplex, killing 12 people and wounding 70.

He could face the death penalty if convicted.

The prosecution wrapped up its case last week after calling more than 200 witnesses, including first responders, survivors and two court-appointed psychiatrists, both of whom concluded Holmes was sane when he planned and launched the attack.

The defense attorneys’ first expert witness, psychiatrist Jonathan Woodcock, said that when he examined Holmes in jail on their behalf four days after the rampage he was startled to hear the defendant tell him he was “bored.”

“I found that absolutely extraordinary,” Woodcock told jurors, adding he diagnosed Holmes to be severely mentally ill, suffering from psychosis, delusions and “emotional flattening.”

Asked by public defender Daniel King whether Holmes had the capacity to tell right from wrong, or to act with intention and after deliberation, Woodcock said that he did not.

During cross-examination, District Attorney George Brauchler repeatedly challenged the psychiatrist’s analysis, noting that Woodcock had met with Holmes for fewer than three hours.

“He has potentially a motive to want to tell you things that will help him in that situation, is that fair?” the prosecutor asked him in one of several testy exchanges.

Woodcock agreed that it was.

The defendant, who carried out the murders wearing a gas mask, ballistic helmet and listening to loud techno music through headphones, first hurled a teargas canister into theater nine at the Century 16 cinema in Aurora, an eastern suburb of Denver.

He then opened fire with an automatic rifle, shotgun and pistol. Prosecutors say he did it because he had lost his career, his girlfriend and his purpose in life, and that he had a longstanding “hatred of mankind.”

Holmes’ public defenders say their client suffers from schizophrenia, that since he was in high school he has heard voices in his head commanding him to kill, and that he was not in control of his actions.

Despite the overwhelming evidence that the California native was solely responsible for the massacre, a conviction and then death sentence is far from certain, said former veteran Denver prosecutor Craig Silverman.

“It only takes one juror to derail this death penalty train,” said Silverman, who prosecuted the last defendant in the city to receive a capital punishment sentence.

Under Colorado’s death penalty statute, a defendant can be found not guilty by reason of insanity if a person cannot tell right and wrong, or if a mental disease prevents the individual from forming the “culpable mental state.”

In a videotaped sanity examination shown to jurors by the prosecution, Holmes indicated that he knew he would go to prison if caught, and that he now “regrets” the shootings.

A key defense witness will be psychiatrist Raquel Gur, director of the Schizophrenia Research Center at the University of Pennsylvania.

Gur, who once examined Unabomber Ted Kaczynski and Tucson mass shooter Jared Loughner, and who was consulted by the White House following the 2012 Sandy Hook Elementary School massacre, interviewed Holmes in the months after the rampage.

Public defenders will likely argue that Gur’s diagnosis is more valid than those of the two court-appointed psychiatrists, since she met Holmes sooner after the massacre than they did, and before he was so heavily medicated.

“The defense psychiatrist may also have performed some physiological testing, such as brain imaging, that could bolster their case,” Silverman said.

If the jury cannot reach a unanimous verdict in the trial’s guilt phase, resulting in a hung jury and mistrial, prosecutors could retry the case.

But if there is a conviction, the defense need to convince just one juror to spare Holmes’ life at the sentencing phase, and if that happens “then it’s game over,” Silverman said.