Nathan P. Sweeney, 44, of DeKalb has been charged with reckless homicide and DUIin connection with 35-year-old Christina Musil's death.
Sweeney was initially was cited for failing to reduce speed to avoid an accident, improper lane usage and operating an uninsured motor vehicle in the crash that killed the deputy while she was on duty.
ISP said they conducted a traffic crash investigation at the request of the DeKalb County Sheriff's Office and determined Sweeney was under the influence of drugs at the time of the crash. The DeKalb County State's Attorney's Office has charged Sweeney with three counts of aggravated DUI and one count of reckless homicide.
Sweeney is currently being held at the Ogle County Jail.
The visitation and funeral arrangements for Musil will be held Thursday.
Musil was killed last Thursday night, when a motor vehicle service truck police say Sweeney was driving ran off the road and crashed into the back of her squad car.
She joined the sheriff's office five years ago, and served in the Army National Guard.
She leaves behind three young children.
The DeKalb County Sheriff's Office administration will be closed Thursday for the services, and will reopen at 8 a.m. Friday.