PLYMOUTH TOWNSHIP (WWJ/AP) – A metro Detroit teenager and her adult boyfriend will stand trial separately on charges that they plotted to kill her family.

WDIV-TV reports that 23-year-old Michael Rivera heads to trial on July 20. The trial for 15-year-old Roksana Sikorski, charged as an adult, is set for Oct. 26.

READ MORE: Science of Weather: Sea Life Michigan Turtles

Each is charged with attempted murder and conspiracy in the Oct. 17, 2014, attack in Plymouth Township.

Prosecutors say Sikorski stabbed her 12-year-old brother multiple times in the neck while Rivera was outside her family’s home, on Glenmore Court, sending her instructions via text message.

According to investigators, Rivera guided the girl, advising her on whether the knife she had was enough to do the job. Other messages included a diagram of the neck, instructions to cut it “like a tomato,” and to make sure the victims stopped breathing, according to reports.

Michael Rivera, right. is seen leaving court on Oct. 31.(credit: Mike Campbell/WWJ)

Michael Rivera, right. is seen leaving court on Oct. 31.(credit: Mike Campbell/WWJ)

READ MORE: Motown Museum Set To Reopen This Weekend With Expansion Project Near Completion

The boy’s screams alerted family members, who interrupted the stabbings as Sikorski and Rivera fled. The boy was hospitalized, but survived the attack.

Investigators believe the pair plotted the attack as part of a plan to run away together. Sikorski’s parents have said she and Rivera, whom she met on Facebook, were involved in a sexual relationship.

Court documents show Rivera also is charged with third-degree criminal sexual conduct involving a person age 13 through 15.

Sikorski was 4-years-old when she, along with her sibling, was adopted from Poland where her lawyers says she suffered abuse.

Attorney Leslie Posner said the girl suffers from RAD or reactive attachment disorder, a rare but serious condition that occurs in children who have been neglected and are unable to form a healthy emotional attachment with their caregivers.

MORE NEWS: Senate GOP Facing Criticism Following Insulin Cap Vote

TM and © Copyright 2015 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2015 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.