Attorney John Demas filed the claim Wednesday against Sacramento County's Child Protective Services on behalf of Kyle Ramirez. It accuses CPS workers of ignoring signs of abuse for seven years.
When Ramirez was 16, he escaped his abusers and showed up at a Tracy fitness center in 2008, looking emaciated, covered in bruises and wearing a shackle around his ankle.
Four people, including his legal guardian, later pleaded guilty or were convicted of abuse charges.
A county spokeswoman declined to comment on pending litigation Wednesday.
If the county rejects the claim, Ramirez can move forward with a lawsuit.