The Grim Sleeper was caught in 2010 through the first successful use of familial DNA searching in the United States: California scientists ran crime scene DNA against the state offender databank looking not for the killer but for a close relative, matched a profile belonging to Lonnie Franklin Jr.’s son, and then had undercover officers collect Franklin’s own DNA from a discarded slice of pizza and utensils he left at a restaurant. That second sample matched the crime scene profile, and Franklin was arrested at his South Los Angeles home on July 7, 2010.1State of California – Department of Justice – Office of the Attorney General. Brown’s Forensic Experts Identify Grim Sleeper Serial Killer Suspect Through Unprecedented Use of Familial DNA
Why Conventional DNA Searches Had Failed for Decades
The killings began in 1985. Between then and 1988, seven women were shot in South Los Angeles, most with the same .25-caliber semiautomatic handgun. Detectives recovered DNA from sexual assaults committed just before the murders, but the technology was new, there was no national database, and traditional leads went nowhere. The murders then appeared to stop for roughly fourteen years, which is what earned the unknown killer the nickname “Grim Sleeper.” Similar killings resumed in 2002 and continued through 2007.
Even with a full crime scene DNA profile in hand, standard database searches produced nothing. The FBI’s CODIS system was built to flag exact matches between crime scene DNA and profiles of convicted offenders already in the system. If the actual perpetrator’s DNA wasn’t there, the search returned nothing useful, and CODIS wasn’t built to systematically detect or rank near-misses that might indicate a relative.2National Institute of Justice. Understanding Familial DNA Searching: Coming to a Consensus on Terminology Finding a relative required different software running outside CODIS entirely, and until 2008 no state had authorized that kind of search.
The Familial DNA Search That Named a Suspect
In April 2008, then–California Attorney General Jerry Brown pushed through the country’s first official policy allowing familial DNA searches, setting protocols for when and how the technique could be used.3State of California – Department of Justice – Office of the Attorney General. California’s Familial DNA Search Program Identifies Suspected Grim Sleeper Serial Killer The premise was simple. Parents and children share about half their DNA, and full siblings share a comparable amount, so a close relative of the killer sitting in the state offender databank would show enough overlap with the crime scene profile to stand out from unrelated people.
The mechanics were more involved. Forensic scientists at the California Department of Justice’s Richmond crime lab used specialized software to scan the state DNA databank for profiles sharing enough genetic markers with the Grim Sleeper’s crime scene DNA to plausibly belong to a first-order relative — a parent, child, or sibling of the perpetrator. Candidates were statistically ranked, and a dedicated Familial Search Committee reviewed the results before any name went to investigators.2National Institute of Justice. Understanding Familial DNA Searching: Coming to a Consensus on Terminology
The break came after Lonnie Franklin Jr.’s son was convicted of a felony weapons charge in 2009 and his DNA was entered into California’s databank for the first time. When the familial search ran, his profile ranked high on the list of possible relatives of the Grim Sleeper. Scientists then compared Y-chromosome DNA, which passes from father to son, between the database match and the crime scene profile. The Y profiles matched, strongly indicating a paternal relationship.1State of California – Department of Justice – Office of the Attorney General. Brown’s Forensic Experts Identify Grim Sleeper Serial Killer Suspect Through Unprecedented Use of Familial DNA Investigators corroborated the lead with other information, including mapping Franklin’s residence against the murder locations, and concluded he was a viable suspect.
Confirming the Match With Discarded DNA
A familial hit points at a family, not at one person. Investigators still needed Franklin’s own DNA to prove he was the Grim Sleeper, and they wanted it without alerting him. An undercover team followed him and, after he ate at a restaurant, collected a discarded piece of pizza along with silverware and a glass he had left behind. DNA extracted from those items matched the crime scene profile.
The collection was legal under California v. Greenwood, in which the U.S. Supreme Court held that the Fourth Amendment does not prohibit the warrantless search and seizure of items voluntarily discarded in a public setting, because a person who leaves belongings for others to take has no reasonable expectation of privacy in them.4Justia Law. California v Greenwood, 486 US 35 (1988) The Court’s reasoning covered trash left at a curb because it is “readily accessible to animals, children, scavengers, snoops, and other members of the public.” Once Franklin walked away from his meal, the DNA on those items was fair game.
Arrest, Trial, and Sentence
Franklin was arrested at his South Los Angeles home on July 7, 2010, at age 57. When police searched the house, they found approximately 160 photographs of women, many of whom could not be immediately identified, and the LAPD later released the images publicly to determine whether any of the women were additional victims.
At trial, prosecutors presented DNA evidence linking Franklin to the murders along with ballistic evidence tying the same .25-caliber handgun to seven of the victims. Enietra Washington, the only known survivor of a Grim Sleeper attack, testified about her ordeal from nearly three decades earlier. On May 5, 2016, a jury convicted Franklin of ten counts of first-degree murder, covering nine women and one teenage girl, along with one count of attempted murder. On August 10, 2016, Superior Court Judge Kathleen Kennedy sentenced him to death, reading each victim’s name aloud and repeating after each, “You shall suffer the death penalty.”
The sentence was never carried out. Franklin was found unresponsive in his single cell at San Quentin State Prison on March 28, 2020, and pronounced dead shortly after. He was 67, and the cause of death showed no signs of trauma.5California Department of Corrections and Rehabilitation. Condemned Inmate Lonnie Franklin Dies
Why the Method Remains Contested
The Grim Sleeper case is often cited as proof that familial DNA searching works, and it also drew the objections that have followed the technique ever since. A familial search effectively turns every person in an offender database into a genetic pointer to their relatives, people who were never convicted of anything and never consented to being searchable. Franklin’s son was in the databank because of his own felony conviction, but the search’s real target was his father.
Critics argue the practice resembles the kind of broad, suspicionless search the Fourth Amendment was designed to prevent, and that DNA is unusually intimate because one person’s profile implicates hundreds of biological relatives who never chose to participate. Supporters counter that it is a logical extension of the long-standing police practice of interviewing a suspect’s family, and they point to Maryland v. King, in which the Supreme Court held that collecting DNA from arrestees is a reasonable booking procedure under the Fourth Amendment, comparable to fingerprinting.6Justia Law. Maryland v King, 569 US 435 (2013) That ruling did not directly address familial searching. Only a handful of states have adopted formal policies authorizing it, and the rules vary by jurisdiction, so what worked in California in 2010 is not automatically available to investigators elsewhere.