RHINELANDER, Wis. » A teenager accused of killing her mother and stepfather has pleaded insanity in a northern Wisconsin courtroom.

Seventeen-year-old Ashlee Martinson pleaded not guilty by reason of mental disease or defect in Oneida County court Monday.

WSAW-TV reports the court will appoint a psychologist to evaluate Martinson before her trial. Her next court appearance is Sept. 28.

She’s accused of fatally stabbing 40-year-old Jennifer Ayers and shooting 37-year-old Thomas Ayers at the family’s home in near Three Lakes last March. Investigators say Martinson confined her three sisters in a room before fleeing to Indiana with her boyfriend. Court documents say the Ayers were killed the same day they warned Martinson’s 22-year-old boyfriend to stay away from her because she’s a minor.

The sisters, ages 2 to 9, were not hurt.