THE MAIN SUSPECT in last year’s shootings at a Colorado cinema has entered a plea of not guilty, by reason of insanity.

James Holmes is accused of shooting dead 12 people and wounding 70 more in a theatre in Aurora, at a midnight premiere screening of the Batman film ‘The Dark Knight Rises’ last July.

Judge Carlos Samour accepted the plea after reading out a list of conditions, including that the 25-year-old agree to undergo a court-ordered “sanity examination.”

The tests, to determine if Holmes is indeed insane, is likely to take several months.

Prosecutors say complex preparations allegedly made by Holmes before the shootings show that he knew exactly what he was doing, and that he understood how his intentions were wrong.

The trial judge initially entered a ‘not guilty’ plea on Holmes’s behalf in March, when lawyers for Holmes said they were not yet ready to enter a plea.

At a new hearing in May, Holmes’s court-appointed attorney Daniel King said he was willing to enter an insanity plea, but the judge said he would not yet formally accept the change of plea.

In court today, however, the judge read out an five-page, 18-point advisement which defined the applicable test for insanity, and listed what was required of Holmes and his lawyers.

After reading the advisement, the judge asked Holmes if he had any questions, and the accused replied: “No.”

The judge ordered Holmes to be sent to the Colorado State Mental Institute in Pueblo, Colorado. He will likely be moved there from jail in a matter of weeks, and could stay there for a month or two.

The judge said there was “no doubt on the part of the defence attorneys as to Mr Holmes’ ability to understand the proceedings.”

Witnesses said Holmes threw smoke bomb-type devices before opening fire in the theatre with weapons including an AR-15 military-style rifle, a 12-gauge shotgun and a .40-caliber pistol.

Prosecutors are pursuing the death penalty in the case, in which Holmes faces 166 counts of capital murder and attempted murder.