The victims' bodies were found in central Ohio nearly two months ago after suspect Matthew Hoffman allegedly told police where to look.
The indictment returned today by a Knox County grand jury charges Hoffman with aggravated murder, burglary, kidnapping, rape, tampering with evidence and abusing a corpse.
If convicted, the 30-year-old unemployed tree trimmer could face life in prison without parole. Prosecutors are not seeking the death penalty, because of the wishes of the victims' families, The Associated Press reported.
The bodies of Stephanie Sprang, 41, Tina Herrmann, 32, and Herrmann's 11-year-old son, Kody Maynard, were located in a wooded area in mid-November. The remains were stuffed inside garbage bags that had been placed in a hollow tree. The victims had been missing for a week before the bodies were discovered, police said.
The indictment alleges Hoffman murdered the victims during a Nov. 10 burglary at Herrmann's home in Howard, about 60 miles northeast of Columbus.
Hoffman was previously charged with kidnapping after Herrmann's 13-year-old daughter was found in the basement of his Mount Vernon home on Nov. 14. The girl was wounded, tied up and gagged, police said. The indictment alleges she was also raped.
During a Nov. 18 news conference, Knox County Sheriff David Barber said investigators found the victims' bodies based on information received from Hoffman.
Authorities have yet to offer a motive in the case. Barber previously said Hoffman had been watching the family but did not elaborate.
Hoffman, an ex-con who served prison time in Colorado for arson and other charges, is being held in the Knox County jail on $1 million bond, the AP reported.