One of the two teenage girls accused of trying to plot a murderous attack at Mountain Vista High School is set to appear in court Tuesday.

Brooke Higgins was 16 when prosecutors say she and Sienna Johnson planned their attack. Both teens were charged as adults with conspiracy to commit first-degree murder under extreme indifference and conspiracy to commit first-degree murder after deliberation.

Their attorneys want the case moved back to juvenile court.

PREVIOUS STORY: Mountain Vista case moves forward

PREVIOUS STORY: Cases against teens who threatened Mountain Vista High School delayed indefinitely

Higgins and Johnson were taken into custody on Dec. 12, 2015 after Douglas County Sheriff’s investigators – acting on a tip – uncovered the alleged plot.

Numerous documents in the case remain sealed, and the full scope of what happened is not clear.

According to prosecutors, the girls had been planning to carry out the attack the week after they were arrested.

Higgins' attorneys say the case is based almost entirely on entries in her journal, which was written at the urging of the girl’s therapist.
Mountain Vista, located in Highlands Ranch, is home to roughly 2,200 students.