Yesterday, Shanann's family sat in the front row of the court as they listened to Watts enter his pleas.
Investigators claimed in the documents that Watts admitted to police that he killed his wife.
Breaking - Chris Watts to take a plea deal to killing his pregnant wife and two daughters.
Rourke said he hoped the agreement would bring some measure of closure for the family, who were present during the court hearing and the press conference.
As part of the sentencing agreement, Watts will spend the rest of his life in prison for the first-degree murder charges. But he told police that he strangled her in "a rage" when he discovered she had strangled their two daughters after he sought a separation.
Rourke said he described "extraordinary delays" in carrying out the death penalty in Colorado since Gov. John Hickenlooper's 2013 decision to block the execution of Nathan Dunlap.
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Their bodies were found hidden in a Colorado oil field, news accounts say, with Shannan Watts buried in a shallow grave and the girls dumped into an oil tank.
"That, to me, was the most important consideration in deciding how to proceed with this case", Rourke said. The victims' family agreed to those terms, the district attorney's office added. The three bodies were found on property near Roggen owned by Anadarko Petroleum Co., where Watts worked as an operator until August 15.
Within days, Watts was arrested and the bodies of his wife and children were recovered. "The spotlight shines directly where it belongs: On him".
Watts' defense attorneys came to the prosecution weeks ago with proposals for plea deals, according to Rourke, though he doesn't know why they did.
Asked if a motive has been determined in the case, Rourke said that investigators believe they have a "partial motive" and Rourke said he would have more to say about that following the sentencing, which is scheduled for November 19.
Colorado law requires that a first-degree murder conviction brings a mandatory life sentence without the possibility of parole.
"Sandra said it best when she said: 'He made that choice to take their lives".
"What I can tell you most affirmatively today, by what happened in the courtroom, is the spotlight that he tried to shine on Shanann falsely, incorrectly and frankly a flat out lie has been corrected", Rourke said.