Analysts initially expected Mr Holmes to enter a plea of not guilty by reason of insanity.

BBC: Aurora shooting: Not guilty plea entered for James Holmes

So she entered a plea of not guilty by reason of insanity.

NEWYORKER: A Loaded Gun

In court documents, Holmes' attorneys had suggested that they might enter a plea of not guilty by reason of insanity for the shooting rampage at the theater that left 12 people dead and 58 injured on July 20, 2012.

CNN: Judge enters not guilty plea for accused theater shooter

"If he enters the not guilty by reason of insanity plea, he's going to be examined by state doctors and any statement he makes to those state doctors are given to the prosecution for potential use later, " Beller said.

CNN: Colorado theater shooting suspect could plead insanity

If Holmes does change his plea to not guilty by reason of insanity, Colorado law gives prosecutors access to some of his medical records.

WSJ: Reporter in Colo shootings fights order to testify

The notebook Winter reported on could play a key role in determining Holmes' fate, especially if he changes his plea to not guilty by reason of insanity.

WSJ: Reporter in Colo shootings fights order to testify

Holmes can still change his plea to not guilty by reason of insanity, and he can wait to do so until after prosecutors announce whether they will seek the death penalty.

NPR: Colo. Judge Enters Not Guilty Plea For Holmes

An insanity plea is at the intersection of law and psychology or psychiatry.

FORBES: Holmes Wants to Plead Insanity For Colorado Theater Shooting. What Does Insanity Mean?

Actually, he first claimed the killing was in self-defense (his father was 83), but later changed that plea to one of Red-Bull-induced temporary insanity.

FORBES: Prosecutors Taking Another Look at "Red Bull" Murder Defense

The judge entered a not guilty plea on Holmes' behalf but said the defense could ask to change that to not guilty by reason of insanity if Holmes chooses.

WSJ: Reporter in Colo. shootings seeks delay in hearing