The cases against two 16-year-old girls accused of planning a murder plot at Mountain Vista High School have been delayed indefinitely.

Brooke Higgins was scheduled to be in court Monday morning for a three-day hearing, but it was vacated at the last minute because the Colorado Supreme Court has not settled appeals filed in both her case and the Johnson’s.

Higgins and Johnson were both charged as adults with conspiracy to commit first-degree murder under extreme indifference and conspiracy to commit first-degree murder after deliberation.

Prosecutors allege Higgins and Johnson were working together to obtain weapons and carry out a murderous attack at their school around Christmas 2015.

Attorneys for Higgins filed an appeal earlier this year, arguing that Douglas County District Judge Paul King made a mistake when he decided not to suppress a psychological examination of the girl. That examination had been ordered by another judge.

The Supreme Court issued what is known as a “show cause” order, requiring prosecutors to explain why King’s ruling was proper.

The Supreme Court issued a similar order in the Johnson case.

In her case, King ruled that Johnson waived the confidentiality of her mental health records when her attorneys filed a motion in an effort to move the case back to juvenile court. Johnson appealed that ruling – and King’s order that she submit to an involuntary psychological evaluation.

Because the Supreme Court hasn’t ruled, this week’s hearing for Higgins, where prosecutors were expected to lay out enough of their evidence to convince Judge King that the case should go to trial, is on hold indefinitely. Also pending is a request to transfer her case back to juvenile court.

Johnson was scheduled to be in court for a three-day preliminary hearing beginning June 14, but it has also been delayed indefinitely.

At a previous hearing, prosecutor Deb Wrenholt said Higgins was infatuated with the two teens who murdered a dozen students and a teacher at Columbine High School – and alleged she had used her cellular phone to research how to buy a gun. Wrenholt also said Higgins warned a friend she would text her the day of the shooting so she could stay home.

The two girls were taken into custody 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 the alleged plan is not clear. What is known is someone sent a text message about the alleged conspiracy to Douglas County, using a system known as Text-A-Tip which was established in the wake of the Columbine tragedy. After looking into it, sheriff’s investigators determined it was credible and took both girls into custody that same day. According to the tip, the girls were planning to carry out their plot the following week.

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.

Contact 9NEWS reporter Kevin Vaughan with tips about this or any story: kevin.vaughan@9news.com or 303-871-1862.