James Holmes

A Colorado judge entered a not guilty plea Tuesday on behalf of James Holmes, the alleged gunman  accused of shooting up a movie theater in Aurora, Colo., last summer during a screening of The Dark Knight Rises.

Judge William Sylvester entered the plea after Holmes' lawyer, Daniel King, said his client was not ready to plead, despite the fact that his court appearance had been delayed several times since the shooting occurred in July, The Associated Press reports.

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Prosecutors argue that Holmes planned the massacre, in which 12 people were killed and 70 others were injured, for months. He is charged with 24 counts of murder (two counts for each fatality), 116 counts of attempted first-degree murder, one count of possessing an explosive device, and one count of violent crime.

Refusing to enter a plea may have been a strategic move on the part of Holmes' defense team to avoid the death penalty, the AP reports. If the prosecution decides to pursue capital punishment, Holmes can still plead insanity and would be sentenced to life in a mental institution rather than being executed if convicted, legal experts tell the AP. The prosecution will announce whether they're seeking the death penalty on April 1.

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On Tuesday, King said that the defense's work on the case is "ongoing," and indicated that it might include a mental evaluation of Holmes, the AP reports. Last week, the defense team said that Holmes was taken to a psychiatric ward in November because he was considered a threat to himself.

Holmes did not speak during Tuesday's court appearance, according to the AP. His parents were also present in the courtroom.