Sienna Johnson, second teen in Mountain Vista shooting plot, pleads guilty to conspiracy, menacing

DOUGLAS COUNTY, Colo. – Sienna Johnson, one of two teens accused in a deadly plot to kill fellow students and staffers at Mountain Vista High School in December 2015, will serve time in state youth corrections facilities after reaching a plea deal with prosecutors.

Johnson on Wednesday pleaded guilty to a juvenile count of conspiracy to commit murder and an adult count of felony menacing.

She will serve five years in the Division of Youth Corrections on the conspiracy charge, and will not get credit for any time she has already served since her arrest.

On the menacing charge, the two sides agreed that Johnson will serve four years of probation upon her completion of her youth corrections sentence.

Though the conspiracy to commit murder charge is the same that Johnson’s accomplice in the plot, Brooke Higgins, pleaded guilty to last year and was sentenced for in February, Johnson agreed to a longer sentence than Higgins, though Higgins' sentence carries different parameters.

Higgins was sentenced to three years in Youth Corrections, but received credit for 409 days served. She was also assigned four years of probation and mental health treatment upon her release, as was Johnson.

As a stipulation of her probation on the menacing charge, Johnson will have to go through a drug and alcohol evaluation and a mental health evaluation upon her release from the Division of Youth Corrections.

She won’t be able to contact Higgins, and her computer and electronic devices will be monitored by a probation officer. She won’t be able to contact any witnesses or possess and weapons.

A judge will review her status once she turns 21, and will decide to either keep her in custody but transfer her to the adult Department of Corrections, or begin her probation period.

"Our goal was to try to put her in a similar circumstance to Brooke, and that circumstance was to make sure that the community was protected for as long as possible, but giving her the maximum amount of supervision and incentive to comply with all the requirements of her sentence,” said 18th Judicial District Attorney George Brauchler. "They didn't want that. They wanted something else that provided her a little more protection.” 

"They didn't want that risk, instead they wanted something different and the different thing we came up with was the guarantee of a felony conviction which will be with her forever." 

Johnson was brief in her responses to the court, often answering only with one-word answers. She hung her head as her plea deal was read to the court.

"This case was extremely troubling for everyone involved … I mean the prosecutors who worked the details of this thing and went through the thousands of pages of discovery were convinced that both of these juveniles represented a certain level of risk that was unacceptable in our public schools, in schools—anywhere," Brauchler said.

Johnson and Higgins idolized Columbine High School killers Eric Harris and Dylan Klebold, and the two planned to carry out a shooting at the Highlands Ranch school a week before Christmas because it would be “the most traumatic” for people, according to their arrest affidavits.

The plan included Johnson first killing her mom and sister and then heading to the school. After shooting up the school, the teens planned to kill themselves.

“Brooke Higgins wrote that many people deserve to be shot, needed to get a gun and then stated it was good she didn’t have one because she’d be dead or others would be,” the affidavit showed.

The teens planned to change the date of the shooting until after the new year to give them time for target practice, the affidavit read. Prosecutors allege Johnson had already bought a BB gun.

"We took this thing seriously; I'll be honest with you, the juvenile justice system creates serious challenges for us. I don't control the fate of these cases the way I do with adult cases," Brauchler said. "This wasn't just a couple kids sitting around saying what if, this was more than that." 

"At the end of the day I have great hope that both of these girls end up growing up to be responsible law abiding members of society that pose a risk to no one, we can't say that today." 

Though her sentence has already been stipulated, Johnson’s sentencing hearing is scheduled for Friday, Aug. 11. She will turn 18 in October.

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