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Prosecutors on Monday formally charged James Holmes with 24 counts of murder in connection with the horrific movie theater shooting in Aurora, Colorado that killed 12 people and injured dozens more.

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The former doctorate neuroscience student -- who appeared in court on Monday -- was charged with two counts for each of the individuals he is accused of killing. He was also formally charged with 116 counts of attempted murder and one count of possession of explosives.

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The 24-year-old Holmes was arrested July 20 outside the theater complex where the massacre occurred during a midnight showing of The Dark Knight Rises.

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Defense lawyers are expected to pursue an insanity defense on behalf of Holmes.