Christian Gerhartsreiter, 52, was convicted in April of killing his landlord, John Sohus, who went missing in February 1985 together with his wife Linda.
The remains of Sohus were found nine years later in the backyard of his home in an upscale Los Angeles neighbourhood.
Prosecutors believe the German also killed Linda Sohus, but he was only charged with one murder.
When the couple vanished, Gerhartsreiter was living in a guest house owned by the victim's mother.
The defendant - clad in a blue prison jumpsuit, his face visibly thinner - again proclaimed, as he has in the past, that he was not guilty before Judge George Lomeli read out the sentence in Los Angeles Superior Court on Thursday.
"I would like once again to reassert my innocence... I didn't commit the crime," Gerhartsreiter said.
A spokeswoman for prosecutors said Gerhartsreiter would be allowed to make his first request for parole once he has served 85 percent of his minimum prison sentence of 27 years.
The hearing began with Lomeli and Gerhartsreiter, who represented himself, debating a motion by the defendant for a new trial - one that the judge ultimately rejected.
Several members of the Sohus family, including the victim's sister, were present in court. "It's been a very long storm but it's almost, almost over," Ellen Sohus said. "Why did you kill John? Where is Linda? I imagine Linda is dead and I think that you're responsible for her death."
After the alleged crime, Gerhartsreiter moved to the East Coast state of Connecticut and changed his name a number of times, eventually becoming Clark Rockefeller and getting married, fooling his wife for 12 years.
Gerhartsreiter - who also pretended to be a Hollywood producer and an English aristocrat during his years evading arrest after the killing – came to the United States more than three decades ago.
For more than 10 years, he lived without a driver's licence or bank account, never signed a lease and would not even take a flight for fear he would be recognized.
He was finally arrested in 2008 and jailed while awaiting trial. He had already been sentenced to five years behind bars in 2009 for kidnapping his seven-year-old daughter.
In closing arguments in April, prosecutor Habib Balian rejected the defence's claim that Sohus's missing wife Linda could just as easily have killed her husband.
Defence attorney Jeffrey Denner had questioned a key piece of prosecution evidence - two plastic bags wrapped around Sohus's skull, each from a US university where the German had studied.
Gerhartsreiter would have to be "one of the stupidest murderers in the history of Southern California" if he killed Sohus and then wrapped the dead man's head in bags clearly linked to him, Denner told the court.
Denner admitted, however, that Gerhartsreiter was "not an easy guy" to defend. "How he went through life didn't make him very likeable... But that doesn't mean that he is a killer," he said.