(CNN) -- Los Angeles police are saying they've arrested a serial killer known as the Grim Sleeper using familial DNA, or the comparison of one's unique genetic code with a relative's unique code.
Police say they found the man accused of killing 11 people -- in murders dating back to 1985 -- by comparing DNA found at some of the crime scenes with the DNA of the suspect's son, who was in a California lock-up. The son's DNA led them to the father, and police are sure they've solved the case.
Familial DNA is a controversial crime-solving method.
Proponents say it helps police identify suspects who wouldn't be on the radar of the police, people who have never been arrested.
Critics argue the use of familial DNA is a violation of privacy. They contend that relying on that type of testing can bring scrutiny to innocent people simply because they are related to a suspect.
Defenders say it's a tool that can point police in the right direction.
"Familial DNA testing is a solid first step grounded in biology, statistics and genetics that leads you to a suspect which traditional investigative work can seal," said Mitch Morrissey, the district attorney of Denver, Colorado, and a nationally outspoken proponent of familial searches.
On Wednesday, LAPD announced it had arrested the man they believe is the Grim Sleeper, 57-year-old Lonnie David Franklin Jr.
The serial killer was nicknamed the "Grim Sleeper" because of a 12-year break between murders -- and then began to kill again.
The killer left his DNA either on victims' bodies or at the scene itself.
In 2009, LAPD Det. Dennis Kilcoyne, who led a special unit assigned to find the Grim Sleeper, expressed frustration with knowing who the killer was, but only in a language of numbers and dashes.
"We've got this beautiful DNA profile -- all these dashes and dots, and this and that, but there's no name to go with it," Kilcoyne said. For years, the detectives followed leads the traditional way.
Then, in 2008, California Attorney General Jerry Brown approved running familial searches through the state's DNA databank, the third-largest in the world with 1.5 million genetic fingerprints of state felons.
Then, last month, police said they found Franklin by running a random comparison search throughout the California prison system, which keeps prisoners' DNA. That search led detectives to Franklin's son Christopher, who had been convicted on a weapons charge.
"Here was a scenario where you had science and old-fashioned police work solving a crime," said Morrissey.
For the past several years, he has publicly urged the FBI to expand its capacity to search for familial matching in its Combined DNA Index System.
CODIS, as it's commonly known, contains more than 8.3 million offender profiles and 319,601 forensic profiles as of May, the FBI's website said.
The FBI has resisted collecting familial DNA, as have states except for California and Colorado, because there is fear that there would be a backlash by civil rights groups over privacy, said Jeffrey Rosen, a law professor at Georgetown University Law School.
Rosen wrote a comprehensive examination of the issue for Slate, the online newsmagazine. He explains the FBI is concerned that if it began collecting familial DNA from arrestees, the backlash could jeopardize its efforts to keep DNA samples from convicted felons.
Rosen says California is now being challenged in court for obtaining and testing familial DNA from people who are arrested.
"The state is really pushing the envelope legally," he said. "If you're convicted, then there's an understanding that you have limited your rights to privacy. To merely be arrested, some argue you should be able to maintain that privacy.
"The legal side of the issue is interesting, but it's paramount to keep in mind that familial DNA is not a panacea to solving crime. It very rarely leads to solving cases," said Rosen.
"You can consider the success rate in Great Britain, a country that is, worldwide, a leader in this method of investigation."
The European Court of Human Rights has maintained that keeping the DNA of people who are merely arrested is a violation of privacy, said Rosen.
Since 2004, British authorities have conducted dozens of investigations using familial DNA -- at least 70 searches, yielding 18 matches and 13 convictions. According to Rosen, the success rate is estimated around 10 percent.
"That's a low number, but when you're talking about violent cases or high-profile cases, any match is a worthwhile effort," said Hank Greely, a Stanford University Law School professor. Greely is considered a national expert on the ethical implication of DNA testing.
He points to a fiery controversy concerning familial testing -- racial profiling.
The CODIS databank is disproportionately filled with African-Americans, said Greely.
"Race is a big issue; it's a legitimate question to address, and it's a troubling fact," he said. "We can talk all day long about why it is that more African-Americans are arrested, but the fact is that the database reflects that. Inevitably that means familial DNA matching will net more African-Americans than any other group of people.
"This a very hot conversation to be having," he said. "And I'm sure this Grim Sleeper case is only going to bring that on like we've never experienced it before in California."
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