Latest News > 14 July 10 - DNA Matching Technique Is A Powerful Tool For Police

 

For more than 20 years, the Los Angeles Police were unable to identify and arrest the Grim Sleeper, the man who sexually assaulted and murdered at least 10 young women in South Los Angeles, despite having his DNA. They were unable to identify the man who allegedly murdered seven women from 1985 to 1988 and three more after 2002 because his DNA was not among the 1.2 million offender profiles in California's DNA database.



The breakthrough came when California's Bureau of Forensic Services, using a new DNA technique - familial searching - identified a convict in the state's database as a close relative of the killer. Further investigation determined the convict was the killer's son. The police then obtained a slice of pizza the suspect had thrown out. DNA on the pizza matched that of the killer. Last Wednesday, Lonnie D. Franklin Jr. was arrested.



The arrest, one DNA expert said, was a home run. It is also the kind of technology that Connecticut should be prepared to use. Although used in Britain since 2003, familial searching is approved for use in only two states - Colorado is the other. California Attorney General Jerry Brown authorized the use of familial searching two years ago. The Grim Sleeper investigation was its first use.


The DNA profile of the killer was compared with the more than 1 million profiles in the state's database using software that looked for kinship patterns between the killer's profile and those in the database. The software ranked the profiles by the likelihood the offender had a parent-child or sibling relationship with the killer. The profiles most closely associated with that of the killer were then compared with his on the Y chromosome, which all males have and which, in sons, is identical to that of the father. The analysis identified one individual among the 1.2 million offenders who was related to the killer - Franklin's son.



California has procedures to ensure familial searching is used effectively while preserving to the maximum extent an individual's privacy. It limits its application to unsolved cases in which all investigative leads are exhausted and in which there is an urgent public safety concern. Searches are limited to the closest relationships - parent-child and sibling - as they are the most likely to share DNA markers.



It set a very high bar for the quality of the DNA evidence subjected to familial searching. This helps reduce the likelihood of partial matches, which could target individuals not involved in the crime. The possibility of a match must be strong before the offender's identity is released to investigators. Finally, the process is monitored at every step.



Perhaps for those reasons, even critics of aggressive approaches to gathering DNA - Brown will be in court this week to defend California's policy of taking a DNA sample from anyone arrested for a felony - applauded how familial searching was used in the Grim Sleeper case. After Franklin's arrest, an attorney with the American Civil Liberties Union of Southern California said, "From our perspective, if you are going to use familial DNA searching, this is the kind of case you should use it for, and the kind of precautions they took in this case are the kind that should be taken."


As long as DNA databases include the profiles of only a small portion of the population - the 76,000 offender profiles in the Connecticut database represent about 2 percent of the population - there will be serious crimes for which there is DNA evidence that doesn't match any profile in the database.



Connecticut's forensic lab has limited resources and its most pressing task right now is to process evidence from ongoing investigations while working down the large backlog of samples that have to be processed. But familial searching is an important technique that offers the possibility of solving cases that otherwise might remain unsolved. The state should start thinking about the procedures, protocols and software that will be needed so the technique can be used effectively when the need arises.

 


 




 

 

 

 

 

 

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