A spokesman for the L.A. County Sheriff's Department said Lonnie Franklin, Jr., 57, was in an attorney waiting room when inmate Antonio Rodriguez apparently recognized Franklin, broke free as he was being handcuffed by a deputy and punched Franklin a couple of times in the head.
Authorities said the attack happened on July 9. Franklin reportedly suffered minor injuries.
Rodriguez has been convicted of sexually assaulting and killing a 5-year-old girl.
Franklin was arrested July 7 and charged with 10 counts of murder. He allegedly killed seven women between 1985 and 1988.
Court records show that Franklin was arrested at least 15 times for car theft, burglary, assault and other crimes. He was often placed on probation and was never entered into the state's DNA database because his crimes weren't considered serious enough.
Authorities suspect that Franklin may be tied to at least 30 cold cases, and they're going through records to find leads for those cases.
His arraignment was postponed until Aug. 9 at the request of his attorney.
The Associated Press contributed to this report.