CASTLE ROCK — Prosecutors said Kelli Murphy smothered and killed her two young children in May 2011 because she was not going to share custody of them with anyone else.

On Tuesday, a jury agreed.

“This is a woman bent on control,” prosecutor Chris Gallo said during closing arguments. “Controlling her kids, her husband and her divorce … It was Kelli’s way or no way.”

Douglas County District Judge Vincent White immediately sentenced her to two terms of life without parole after the nine men and three women on the jury found her guilty of two counts of first-degree murder after deliberation and two counts of first-degree murder of a victim under 12 years old.

When her sentence was read, Murphy, 43, remained silent and looked forward until she was led from the courtroom.

Throughout the case, prosecutors claimed that Murphy killed her 6-year-old daughter, Madigan, and 9-year-old son, Liam, when she became distraught over her impending divorce from her husband, Robert Eric Murphy.

The severity of the murder charges against Murphy was contingent upon her mental state. The prosecution’s case, argued Tuesday by Gallo, was that Murphy deliberately killed her children.

Gallo said Murphy was a controlling, angry, calculating woman who did not want to share the children with her ex-husband.

“I want 100 percent custody of the kids and 100 percent of your salary,” Gallo told the jury that Kelli Murphy had told Robert Murphy. “I’m going to make your life hell.”

The defense argued that the children’s deaths were accidental because Murphy blacked out from drinking a full bottle of vodka and taking too many pills. Her plan, defense attorney Ara Ohanion said, was to kill herself and make it look to her children like she just fell asleep.

When she awoke, Ohanion said Murphy found the dead bodies of Madigan and Liam face down on their beds and had no memory of what happened, so she cut her own wrists.

“No mother who loved her children the way Kelli did would do this intentionally or knowingly,” Ohanion said.

Ohanian said Murphy felt abandoned and shunned by her family because of the divorce and was becoming more detached, unstable and paranoid in the days leading up to the murders.

“Erratic behavior mirrors erratic thoughts,” said Ohanian, who asked the jury for a reduced charge of reckless manslaughter.

On that day in May 2011, Murphy called 911 about 12 hours after her children were dead, saying she was trying to commit suicide.

A recording of the call played in the courtroom and the jury listened to Murphy tell the dispatcher that she “hurt her two young children.” When asked what happened, Murphy said, “I have to have an attorney.”

Gallo said this proved beyond reasonable doubt that Murphy was sober and conscious enough to know that she would immediately need legal defense for her actions.

But Ohanian argued that it meant just the opposite.

“Requesting a lawyer means she didn’t know what happened,” he said. “She asked the EMT to kill her on the way to the hospital” — she was not in her right mind, he said.

Gallo said the suffocation of the children was far too precise, personal and prolonged to be accidental or the result of a drug-induced black out.

“The manner of death speaks volumes about the intent,” Gallo said. “And it had to happen twice.”

According to police reports, Liam and Madigan’s bodies were found tucked into their beds, in separate bedrooms, with their stuffed animals placed neatly around them.

During the prosecution’s rebuttal, District Attorney Jay Williford acted out the amount of time and planning it would take to separate and kill each child. Pictures of the children’s locked bedroom doors came on a projector. Williford paused and watched the clock.

“Liam is now unconscious,” he said after about 30 seconds. After two minutes, he said, “Liam is now dead.”

Friends and family in the courtroom sobbed in the silence as he counted seconds.

A picture of Liam’s body lying face down on his bed appeared from the projector.

Tuesday would have been his 11th birthday, the prosecution said.

Williford repeated the counting and silence for Madigan. The screen flashed to images of her clenched teeth and fists. Williford said Murphy had to tuck Liam in, arrange his bed and then unlock her daughter’s door to kill her, taking an equal amount of time.

The two sides also brought up a debate about the toxicology report on Kelli Murphy. The defense claimed she had ingested a full bottle of vodka and Ambien, a sleep aid. But the prosecution pointed out that a test performed on Murphy 27 hours after she said she took the substances showed only Benadryl.

The defense said the substances could have been cleared from her system by then.

Though the courtroom was packed to capacity with family and friends, none were able to speak after the conviction. They issued a statement.

“Although nothing can make up for the loss of Liam and Madigan or fill the void that is left by their absence, we are thankful that this chapter is now over and we look to God to help lighten our hearts,” he statement said.

Eric Murphy was not present for the closing arguments or verdict.

Castle Rock Chief of Police Jack Cauley said that he and his officers sought justice for Liam and Madigan since day one, and that it had been served to their full satisfaction Tuesday.

Megan Mitchell: 303-954-1223, mmitchell@denverpost.com or twitter.com/megs_report