The man calls himself Clark Rockefeller, but his real name is Christian Karl Gerhartsreiter.
He was charged Tuesday with killing 27-year-old John Sohus of San Marino in 1985. Sohus' body was discovered nearly a decade later.
An investigation determined he was killed by blunt force trauma to the head. Sohus' wife, Linda, is still missing.
Prosecutors are trying to extradite Gerhartsreiter from Massachusetts to California.
Rockefeller is currently serving a prison sentence there for kidnapping.