Crime and Punishment Criminal Justice

“Familial DNA” and An Arrest in the Grim Sleeper Case

The man who may be responsible for the longest killing spree
in California history was arrested on Wednesday as a consequence of dogged police work and a complex new forensic tool called “familial DNA“—a method used only as a last resort after traditional DNA routes have been tried without success.

Familial DNA allows forensic scientists to use DNA markers to ID possible family members of a perpetrator who has left his or her DNA on the scene, and then to follow all family strands until the killer has been located.

This is precisely what happened in the case of the man believed to be the The Grim Sleeper. (The killer was given this sobriquet by the LA Weekly’s Christine Pelisek, who originally broke the story in 2006 when police were trying to keep the news of the serial murders quiet.)

The alleged killer of at least 11 people, with murders going back 25 years, turned out to be a 57-year-old South LA auto mechanic named Lonnie David Franklin Jr., who was well-liked by his neighbors.

(Once again, the so-called face of evil ends up being all too sadly ordinary.)

The LA Times has some good team coverage of the steps that led to the arrest.

Here’s a clip:

For well over two decades, the killer had eluded police. His victims, most of them prostitutes in South Los Angeles, had lived on the margins of society, and their deaths left few useful clues aside from the DNA of the man who had sexually assaulted them in the moments before their deaths.

A sweep of state prisons in 2008 failed to come up with the killer or anyone related to him. Then, last Wednesday, startling news came to the LAPD: A second “familial search” of prisons had come up with a convict whose DNA indicated that he was a close relative of the serial killer suspected of killing at least 10 women.

Working through the Fourth of July weekend, LAPD detectives drew up a family tree of the prisoner, then began analyzing all the men on it. Were they the right age? Did they live near the murder scenes? Was there anything in their background to explain why the serial killer had apparently stopped killing for 13 years, then resumed in 2003?

From that painstaking process, according to LAPD officials who requested anonymity, the prisoner’s father emerged as a likely suspect. An undercover team was sent to follow him; they retrieved a discarded slice of pizza to analyze his DNA. On Tuesday, they confirmed that it matched the DNA of the suspect in the killings.

(There’s a lot more on the history of the investigation and now the reaction of neighbors, so read the rest.)

A large thank you to all the LAPD officers involved for not giving up.


And just in time, earlier this week NPR’s Talk of the Nation had a story on new research looking at the relationship between brain abnormalities, certain genes and serial killers.

1 Comment

  • I don’t understand this. If regular DNA evidence didn’t lead them to the right person, how could this method?

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