Prosecutors haven't said whether they would accept the offer, and victims and survivors of last summer's shooting massacre left 12 dead and 70 injured differed on what should be done. A trial promises an emotionally wrenching courtroom battle and a debate over Holmes' sanity.
Melisa Cowden, whose ex-husband was killed in the rampage, said she was resolutely opposed to a plea deal.
"He didn't give 12 people the chance to plea bargain and say, 'Let's see if you're going to shoot me or not,' " said Cowden, whose two teen daughters were with their father when he was killed.
Pierce O'Farrill, who was shot three times, said he would welcome an agreement that would imprison Holmes for life.
"I don't see his death bringing me peace," O'Farrill said. "To me, my prayer for him was that he would spend the rest of his life in prison and hopefully, in all those years he has left, he could find God and ask for forgiveness himself."
Prosecutors have said Holmes planned the assault during a midnight showing of "The Dark Knight Rises" for months. Then on July 20, he donned a police-style helmet and body armor, tossed a gas canister into the theater crowd and opened fire.
The plea offer, made by Holmes' lawyers on his behalf earlier this month, was disclosed in a defense court filing Wednesday.
Tom Sullivan, whose son Alex was killed, said he has wanted prosecutors to pursue the death penalty. But he said he wouldn't object to a plea agreement if it avoided a lengthy court battle -- and if Holmes got no privileges in prison.
"That was kind of a sore point with us," he said, referring to privileges such as outside exercise or listening to music. "We didn't think this kind of person should have any kind of privileges except the bare essentials."
Holmes, a former graduate student at the University of Colorado, Denver, was widely expected to enter an insanity plea at his arraignment on March 12, but his attorneys told District Judge William Sylvester they had too many questions about the constitutionality of Colorado's death penalty and insanity statutes to advise Holmes on how to plead.
Sylvester then entered a plea of not guilty on Holmes' behalf but said he could change it later to insanity if he chose. The judge scheduled the trial to start Aug. 5, setting aside four weeks.
Holmes had seen a psychiatrist at the school before the shootings. His lawyers have said he was taken to a hospital psychiatric ward in November because he was considered a threat to himself.