Rubi Ann Martinez, 32, is suspected of allowing 21-year-old Enrique Ramirez Alvarez to ride in the open bed of her 1996 GMC truck, CHP Officer Jon Sloat said.
Alvarez fell out of the truck and may have been struck by another vehicle before a motorist found his body on the highway near the Mendocino Avenue overpass, according to the CHP.
That motorist stopped behind the body so another vehicle would not hit it, and the CHP responded to the scene at 1:40 a.m. Alvarez was pronounced dead at about 2 a.m.
Sloat said an investigation has indicated that Martinez knew Alvarez fell out of the truck but decided not to return to help him or call authorities, and instead allegedly tried to conceal the incident.
A Sonoma County jail spokeswoman said Martinez was booked at 5:30 p.m. Thursday under the name Rubi Ann Ajcalon for hit-and-run causing death or injury, manslaughter with gross negligence, DUI and two violations of probation for felony charges of having insufficient funds and passing fictitious checks.
Sloat said her true name is Rubi Ann Martinez and Ajcalon is an alias.
She is scheduled to be arraigned at 1:30 p.m. Tuesday in Sonoma County Superior Court.
The death was initially thought to be a possible homicide, and the CHP notified Santa Rosa police. When an autopsy determined that the puncture wound in Alvarez's right thigh was from a compound fracture and not a gunshot wound, the CHP took over the hit-and-run investigation.
The CHP is still looking for a vehicle that may have struck Alvarez after he fell out of the truck.
Sloat said this morning that Martinez and Alvarez were friends.
He would not disclose how the CHP identified Martinez as a suspect, but said investigators are interviewing Alvarez's friends and family members.
The Sonoma County coroner's office had initially identified the victim as Enrique Alvarez Ramirez.