Dustyn Frolka was found unconscious Feb. 15 on Interstate 69 in Clinton County's Bath Township, near Lansing. The sophomore was from Owosso.
Authorities have charged three Saline teens with first-degree murder and armed robbery. They are 19-year-old Samantha Grigg, 18-year-old Tyrel Bredernitz and 16-year-old Brendon Heim.
The Lansing State Journal says Bredernitz and Grigg waived their right to a preliminary examination Tuesday in St. Johns.
Grigg lawyer Ron Zawacki says his client is expected to plead guilty to lesser charges April 28. County Prosecutor Chick Sherman says plea negotiations are underway for Bredernitz.