Justin Lenz pleaded guilty on Tuesday to second-degree murder in the May 2012 death of Melanie Koontz. Lenz had been charged with first-degree murder and using a weapon to commit the crime.
Koontz' body was found in Cole Creek under the Blondo Street bridge in May 2012. Prosecutors say she had been strangled. Koontz was a student at Benson High School.
Lenz will be evaluated by a psychologist before he is sentenced on November 6th. He faces 20 years to life in prison.