Catching the Grim Sleeper – An Interview with Rock Harmon

It’s estimated that 80+ people have been murdered by the Grim Sleeper since 1985. He is the longest-operating serial killer west of the Mississippi. He was given the title “Grim Sleeper” by LA Weekly, because he took a 13-year hiatus before resuming killing.



Written by: Tara Luther, Promega


On March 21, 2001, Los Angeles Police Department Chief Bernard Parks instructed detectives to re-examine cold case murder books using new DNA technologies. This uncovered links between several cases attributed to the Grim Sleeper.

Four years later on May 31, 2005, LAPD Detective Cliff Shepherd finds a DNA match between Valerie McCorvey (killed in 2003), Princess Berthomieux (killed in 2002), and a preserved DNA sample taken from Mary Lowe (killed in 1987).

On April 21, 2008, California became the first state to make familial searches legal when the crime scene DNA profile is a single-source profile and where all other investigative leads have been exhausted. Later that year on December 3, 2008, familial search testing was performed in the Grim Sleeper case as no matches were found in law enforcement databases. Unfortunately, the DNA familial testing failed to establish any viable clues to the identity of the Grim Sleeper.


Read our interview with Rock Harmon on how familial searching lead to the arrest of the Grim Sleeper! Share on X


In 2009, detectives caught a break when Lonnie Franklin’s son, Christopher, was arrested and convicted in a felony weapons charge and swabbed for DNA. Detectives were alerted that his DNA was a partial match to DNA found at the Grim Sleeper crime scenes. Detectives then began investigating the son’s relatives and found a match in Lonnie Franklin.

Los Angeles police Det. Dennis Kilcoyne, who headed the investigation, said it was the second time a query was run for familial connections in the “Grim Sleeper” case. From the DNA matches, a tight-circle of law enforcement officers zeroed in on Franklin based on the suspect’s residence, location of the victims, his race and age.

FILE - In this Aug. 23, 2010, file photo, Lonnie Franklin Jr. appears for his arraignment on multiple charges as the "Grim Sleeper" killer, in Los Angeles Superior Court. Relatives of victims will urge a Los Angeles Superior Court judge Friday, Feb. 6, 2015, to set a trial date for Franklin, who is charged with 10 counts of murder, and has been dubbed the "Grim Sleeper" serial killer. Prosecutors are citing Marsy's Law, a voter-approved victim's bill of right, to argue that the right to a speedy trial, guaranteed for defendants, also extends to family members of the victims. (AP Pool/Nick Ut, File)
FILE – In this Aug. 23, 2010, file photo, Lonnie Franklin Jr. appears for his arraignment on multiple charges as the “Grim Sleeper” killer, in Los Angeles Superior Court. (AP Pool/Nick Ut, File)


On July 7, 2010, Lonnie David Franklin Jr. was arrested and charged with 10 counts of murder. According to Los Angeles District Attorney Steve Cooley, detectives had used a piece of discarded pizza with Franklin’s DNA on it to make the link.

For more on the case and how familial searching was used to close the case of the Grim Sleeper, we interviewed Rock Harmon. Rock is a retired Senior Deputy District Attorney for Alameda County, California after 33 years. Currently, Rock is employed as a consultant to numerous law enforcement agencies dealing with such issues as cold case investigation and other issues related to forensic DNA typing.


Who is the Grim Sleeper? Why is this case so monumental?

He was a serial killer in Los Angeles who eluded detection as he had never been included in California’s DNA database because his criminal record was minimal. While he has recently been convicted of many killings, it is suspected that he committed as many more. Solving these murders was California’s first success with familial DNA searching.


Familial Searching was first employed as a tactic to try to identify the Grim Sleeper in late 2008, when it failed. Why do you think the tactic was used then, and then employed again in 2010?

The decision to use familial searching was made upon request by LAPD, recognizing that the cases met the criteria established by CalDOJ. The majority of familial DNA searches do not produce viable investigative leads. When the first search failed to produce a lead the protocol allows for a new search every year, upon request. It was only after the successful outcome of the second search that it was realized why no lead occurred the first time. The son of the killer was not in the database during the first search. He was added soon thereafter. These two searches and their outcomes demonstrate how reliable the complete search/lineage test results are. When the close relative is not in the database no lead is produced. When the close relative is in the database there is almost always just one investigative lead generated.


Police were able to retrieve Lonnie David Franklin Jr’s DNA from a discarded pizza crust after an undercover police officer pretended to be a waiter where Franklin was eating. Why was this evidence admissible when Franklin hadn’t expressly submitted to testing?

The legal phrase that best describes the tactic used to collect Franklin’s leftovers and utensils is called “abandoned dna”. In the US legal precedent is overwhelmingly supportive of what the investigators did in collecting these materials in order to determine if his DNA matched the evidence in these murders. Franklin had an opportunity to challenge the collection as a violation of his 4th Amendment rights and he lost that legal challenge during a pretrial hearing. Most law enforcement agencies rely on this investigative technique for familial DNA searching and for CODIS cold hit follow up.


The defense questioned whether the analysts working on the case had been working on other cases at the same time? Why would this be important?

Much of the cross examination of prosecution DNA experts concerned the “possibility” of contamination, as well as about the presence of other DNA profiles and complicated mixtures on less probative samples. Working on other cases provided an opportunity for cross contamination, but only if the analysts abandoned the normal safeguards that are routine in forensic DNA casework analysis. While this tactic might tend to confuse jurors or contribute to reasonable doubt, it obviously was ineffective in this case. (I actually watched some of the cross-examination.)


The defense also suggested that a nephew of Franklin could have been responsible. Is it possible that another relative could have been the killer and not Lonnie David Franklin? Why or why not?

While anything may be possible, one can easily calculate the unlikelihood of having any such relative’s match the evidence using the number of loci typed in this or any case.


Some have suggested that giving the Grim Sleeper a title and extensive media coverage lead to police devoting more energy to finding the killer. How do you feel the media coverage impacted this case, if at all?

Interestingly investigators often create nicknames for many of their unsolved serial crimes. This was no exception. The practice seems to have appeal to the media and seems to encourage publicity. While publicity occasionally generates investigative leads, it did not in this case. However the publicity and seriousness of the unsolved crimes helped make this a priority for familial DNA searching.


The case of Lonnie David Franklin Jr. is now moving to sentencing. What sentence do you think the jury will return?

The jury selected the death penalty already, an option that remains only highly symbolic in California. In cases such as this one even liberal California jurors continue to select the death penaly.


Familial Searching has been used by California since April of 2008, with the arrest (and subsequent conviction) of the Grim Sleeper in 2010 as one of its most noted accomplishments. What impact (if any) do you think this success will have on other states’ usage of Familial Searching?

Sadly, successes such as this case have done little to encourage other states to adopt the practice. The reasons are unclear as there has been very little open, public discussion of it. There is a hidden, underlying reason for this failure- the number of government labs that have not yet implemented Y-STR typing. This lineage typing is a fundamental part of the familial search process. Those labs which do not provide Y-STR typing can never adopt familial searching, and are unlikely to admit the true reason.


Critics of Familial Searching have argued that Familial Searching will disproportionately target minorities, as they are more prevalent in DNA databases. How would you answer these critics?

Offender DNA databases reflect the racial composition of offenders in states. While these ratios may be disproportionate to society as a whole, they are reflective of those who commit crimes. In that sense, both CODIS and familial DNA searching can be said to disproportionally target minorities.

Because Lonnie Franklin was a serious candidate for the death penalty, there must have been extension challenges made to using familial DNA searching to solve these crimes?

There was absolutely no legal challenge made to the practice of familial DNA searching in this case. This was not because the defense was inept, they tried to use whatever legal or tactical steps to represent Franklin. There is simply no cognizable legal challenge that can be made, and none was made. Had there been a successful challenge he might be a free man today. He is on death row instead.