A judge in Colorado has entered a "not guilty" plea on behalf of James Holmes, the 25-year-old former neuroscience student accused of shooting dead 12 people in a massacre at a movie theatre in Aurora, near Denver, in July last year.

In an odd twist to the closely watched case, Mr Holmes's lawyer told a hearing that his client was not yet ready to enter a plea. The defence couldn't say when it would be content to enter its own plea, but suggested it would take until at least May or June to complete "ongoing work".

Prosecutors demanded the case move ahead and Judge William Sylvester told Mr Holmes he could change his plea to not guilty by reason of insanity at a later date if he wishes to do so. It was recently revealed that Mr Holmes had been admitted to a Denver psychiatric ward for several days in November, where he was held in restraints, because the authorities believed he posed a danger to himself.

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The accused, who now has a beard and long hair, sat quietly in court, watched by his parents. Mr Holmes was a graduate student at the University of Colorado when he allegedly killed 12 people and injured 70 others at a midnight screening of The Dark Knight Rises.