This fifth episode of the Case Studies season of the National Institute of Justice's (NIJ's) Just Science podcast series is an interview with Rockne Harmon, forensic consultant and former senior deputy district attorney for Alameda County, California, who discusses familial DNA searching and its use in the case of the Grim Sleeper Serial Killer.
Background information for the interview indicates that from the mid-1980s to 2007, Lonnie David Franklin, Jr., known as the Grim Sleeper, committed at least 10 murders in California. Although he started killing in the 1980s, large gaps of time between murders and under-used DNA evidence left at the crime scenes made it difficult to identify a suspect. Franklin was arrested in 2010 after investigators used familial DNA searching to connect DNA recovered at multiple crime scenes to one of Franklin's relatives. Rockne Harmon was instrumental in convincing the California Department of Justice to implement familial DNA searching in cold cases, ultimately leading to the arrest of the Grim Sleeper and many other offenders. Much of the Harmon interview focuses on the legal parameters for familial DNA searching, which are set by the states. States may require that familial searching of private, within-state DNA databases can only be done by law enforcement agencies and only after a CODIS search has found no match or familial association. Although familial DNA searching may not render an exact match with crime-scene DNA, it can narrow the suspect to a particular family and guide additional investigative measures to obtain a DNA match. How this was done in the Grim Sleeper cases is discussed in the interview.