James Holmes, accused of killing 12 people in a Denver, Colorado movie theater last July, is expected in court on Tuesday to enter a plea.
Attorneys for Holmes, 25, have indicated that he may plead "not guilty by reason of insanity," the Morning Express reported.
In the event his lawyers do use the insanity plea, a judge has ordered that Holmes be forced to take a "truth serum" and undergo a "narcoanalytic interview" to determine if he was legally insane at the time of the July 20 shootings.
The Associated Press wrote that the drugs administered during a narcoanalytic interview — a decades old process — lowered the inhibition of defendants.
Reuters cited Arapahoe County District Judge William Sylvester as saying the drugs were "medically appropriate."
Sylvester said Holmes also could be given a polygraph examination as part of an evaluation at the state mental hospital.
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However, Holmes' lawyers have said a narcoanalytic interview and a polygraph would violate their client's rights.
According to Reuters, prosecutors have 60 days after Holmes' plea is entered to decide whether to seek the death penalty.
Fifty-eight people were hurt in the rampage at a midnight showing of the Batman film "The Dark Knight Rises" in the Denver suburb of Aurora.
Prosecutors say Holmes spent months carefully planning the attack.
A former neuroscience graduate student at the University of Colorado, Holmes failed oral board exams in June.