The Los Angeles County Sheriff's Department this week said it had concluded Rockefeller was Gerhartsreiter after conducting interviews with people who knew him in California in the 1980s.
Authorities have said Gerhartsreiter lived all around the U.S., including California, Wisconsin and Massachusetts, under aliases including Chris Crowe, Chris Chichester, Charles Smith and Chip Smith.
"Gerhartsreiter is at the center of the longest con I've ever seen in my professional career," said Daniel Conley, district attorney in Massachusetts' Suffolk County.
"As prosecutors, we need more than a photo and a fading memory to walk into court and amend a complaint," he said.
By matching recent fingerprints to those on the old papers, Conley said, "the FBI's fingerprint technicians brought science to bear where mere suspicion had prevailed."
California authorities want to question Gerhartsreiter about the 1985 disappearance of Jonathan and Linda Sohus. Gerhartsreiter rented a guesthouse at the home of Jonathan Sohus' mother in San Marino, a wealthy Los Angeles suburb.
DNA testing is under way to determine whether bones dug up on the Sohus' property several years after their disappearance belonged to Jonathan Sohus. The Los Angeles County Sheriff's Department has labeled Gerhartsreiter a "person of interest," but he has refused to talk to their investigators.
No charges have ever been filed in the disappearance.
Rockefeller's lawyer, Stephen Hrones, has said his client recalls the missing California couple and using the Chichester name while living in California in the 1980s. But he said the man has no memory of being Christian Gerhartsreiter and insists he had nothing to do with the disappearance.