Regardless of whether he pleads insanity, Holmes could get the death penalty or life in prison without the possibility of parole if he were convicted.
Prosecutors have not said if they will seek the death penalty. They must declare their intentions within 60 days of the day Holmes enters his plea.
Last week, Holmes' lawyers asked Sylvester to declare a state law on the insanity plea unconstitutional, saying it violated his Fifth Amendment protection against self-incrimination. They also said they could not give Holmes effective advice on how to plead because of questions they had about the insanity law.
In a ruling released Friday, Sylvester refused to declare the law unconstitutional, saying appeals courts already have upheld it.
He also said he would not address "hypothetical" questions raised by the defense.
Sylvester granted one defense request, for a written explanation of the consequences of pleading not guilty by reason of insanity.
Associated Press writer Colleen Slevin contributed to this report.
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