A Jury in the United States has found “Batman” shooter James Holmes guilty of the Colorado movie massacre that left 12 dead and dozens injured.

The 27-year-old former neuroscience student could now face the death penalty following the decision on Thursday.

In July 2012, Holmes entered a cinema screening of Batman sequel “The Dark Knight Rises” in Aurora, just outside Denver, Colorado and opened fire killing 12 and wounded 70 more.

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Jurors took 13 hours to find Holmes guilty for multiple counts of murder, but are yet to decide whether he should be executed or sentenced to life in prison without parole.

Holmes pleaded not guilty on the grounds of insanity with his lawyers arguing he was unable to tell right from wrong at the time of the attack.

“We can’t separate the mental illness from him or this crime because the mental illness is the sole reason this occurred,” lead public defender Dan King told the court in closing arguments.

However, state psychiatrists found Holmes was sane at the time of the shootings, although they agreed he had struggled with mental illness.

Prosecutor George Brauchler said the gunman was unusually intelligent but socially inept with a deep hatred for humanity.

Throughout the 49 day trial prosecutors argued Holmes made detailed preparations for the attack.

Survivors of the bloody rampage also testified during the trial, describing how they took cover behind movie seats while Holmes opened fire.

Holmes’ defence did not contest that he lobbed smoke bomb-type devices into the cinema and randomly fired weapons including an AR-15 military-style rifle, a 12-gauge shotgun and a .40 caliber pistol.

His apartment was later found to be booby-trapped with an array of homemade explosive devices, which police had to disarm before entering.

-with AAP.