The accused Colorado mass shooter was arraigned on Tuesday.

In a twist, lawyers for James Holmes said he wasn't ready to enter a plea, so a judge did it for him, issuing the standard "not guilty" plea.

Holmes is accused of gunning down moviegoers at the screening of "The Dark Knight Rises" last year.

A dozen people died and 58 others were wounded.

Sanity was expected to be a major part of Tuesday's proceedings.

But as CNN's Ted Rowlands reports, there is a good chance his lawyers could still pursue that defense.

As James Holmes walked into the courtroom Tuesday, shooting victim Marcus Weaver was watching his every move.

"According to what I saw and just being in that same courtroom as the person who committed one of the largest massacres in U.S. history, I feel that he didn't seem out of touch," Weaver said.

Weaver doesn't believe James Holmes is insane, but there's a good possibility his lawyers will be pursuing an insanity defense.

If they do, Colorado law requires James undergo extensive psychiatric testing, which could include not only a lie detector test but also truth serum.

"The person would be given an IV and be given a bit of the medicine and then you start asking them questions and they start talking," says Dr. Max Wachtel, a forensic psychologist.

Truth serum, Dr. Wachtel says, can come in different forms, including sodium thiopental, which is also used in executions to calm a prisoner before a lethal injection.

The problem, says Dr. Wachterl, is truth serum doesn't necessarily work.

"They could be lying, they could be hallucinating and talking about stuff that never happened, they could be making things up, all kinds of things can come out of somebody under the influence of a drug like that," he says.

None of the experts we talked to seem to remember truth serum actually being used to evaluate a prisoner. But Judge William Sylvester has approved the use of it on Holmes, if he pleads insanity, along with a full mental evaluation of Holmes. His lawyers are worried that could end up being used against him.

"If they're seeking the death penalty, then anything he says can not only be used to convict him but to kill him as we'll," says criminal defense attorney David Lane.

James Holmes' parents attended Tuesday's hearing but had nothing to say as they were leaving the courthouse.

CNN's Ted Rowlands adds, prosecutors say they plan to announce whether or not they'll seek the death penalty against James Holmes at his next court appearance, which is scheduled for April 1.