Deputies responded to the area of Route 59 and Diemer Street in unincorporated Antioch around 8:30 p.m. They found a downed 1998 Harley-Davidson Motorcycle and 43-year-old Antioch woman, who was unconscious and unresponsive in the roadway.
The woman, who was a passenger on the motorcycle, was transported to an area hospital with critical, life-threatening injuries.
The motorcycle's driver, 51-year-old Gregory Shaer, of unincorporated Lake Villa, initially told deputies that he was traveling southbound on Route 59 and swerved to avoid hitting a vehicle that turned in front of him, which caused him to lose control of the motorcycle.
The sheriff's department said Shaer did not suffer significant injuries.
Sheriff's deputies then spoke with a 33-year-old woman who said she was traveling northbound on Route 59 in her GMC Acadia when Shaer swerved into her lane of traffic and sideswiped her vehicle.
Sheriff's deputies found signs of alcohol impairment from Shaer and arrested him. He was transported to a local hospital, where samples were taken and sent to the crime laboratory for analysis.
Shaer has been charged with aggravated DUI Resulting in Great Bodily Harm, DUI - Alcohol and Driving in the Wrong Lane of Traffic.
Shaer remains in custody at the Lake County Jail pending his first court appearance Sunday morning.