Prosecutors have said they will seek the death penalty for James Holmes, the man accused of killing 12 people in an Aurora cinema during a screening of The Dark Knight Rises.
Rejecting the defence's team offer of a guilty plea in return for life imprisonment without parole, prosecutors said the defence had not offered a serious deal and were merely trying to rally public support for a plea bargain.
George Brauchler, the Arapahoe County district attorney said: "It's my determination and my intention that in this case for James Eagan Holmes justice is death."
Prosecutors said they had reached out to 800 survivors and families of the victims to make their decision.
Holmes, 25, faces 166 charges of murder and attempted murder for the massacre at a screening of the batman movie last July that left 12 people dead and another 58 injured.
The former neuroscience graduate student's defence team is expected to argue Holmes was legally insane when he went on the shooting spree. A plea deal could still be reached before the case goes to trial next month.
Victims of the shooting have expressed mix of emotions around the latest developments in the case.Bryan Beard, whose best friend Alex Sullivan was killed in the attack, told the Associated Press at the courthouse. "I love the choice, I love it, I love it... I hope I'm in the room when he dies."
Greg Medek, who lost his daughter in the attack, told The Denver Post the best punishment for Holmes is to fight for his life every day.
"The coward needs to go into the general population with the rest of the killers," Medek said. "I want him to go in there and contend for his existence every day. I want him to suffer every day and earn his incarceration."
Pierce O'Farrill, who was shot three times that night, told the Associated Press "All of us victims would be dragged along potentially for years. It could be 10 or 15 years before he's executed.
"I would be in my 40s and I'm planning to have a family, and the thought of having to look back and reliving everything at that point in my life, it would be difficult."
Colorado has executed one person since 1977 and there are currently three individuals on death row, all residing in Arapahoe County.