Prosecutors say they are not ready to accept the offer of a guilty plea from the Colorado cinema shooting suspect in exchange for avoiding the death penalty.
Legal experts say the case pivots on whether James Holmes, 25, was legally insane when he opened fire at the cinema in Aurora, killing 12, in one of the worst mass shootings of last year. Dozens were wounded.
In a court filing, prosecutors criticised defence lawyers for publicising Holmes' plea offer, calling it a ploy meant to draw the public and the judge into what should be private negotiations.
Holmes' lawyers disclosed in a court filing on Wednesday that their client had offered to plead guilty to killing 12 people at a midnight screening of the latest Batman film, The Dark Knight Rises, last July, but only if he would not be executed.
Prosecutors have also criticised comments to the media from Doug Wilson, who heads the state public defenders' office.
George Brauchler, the district attorney, is due to announce on Monday whether he will seek the death penalty for Holmes.
A plea bargain would bring finality to the case fairly early so victims and their families can avoid the prolonged trauma of not knowing what will happen, said Dan Recht, a past president of the Colorado Criminal Defence Bar.
"The defence, by making this public pleading, is reaching out to the victims' families," he said.