The serial killer known as the "Grim Sleeper" eluded police in Los Angeles for some twenty-five years. But last week the LAPD arrested Lonnie David Franklin, Jr. after making a breakthrough using DNA obtained from the suspect's son, a convicted felon. Only Colorado and California allow the unusual type of detection known a "familial," or mitochondrial DNA. Will the Grim Sleeper case lead to increased use of familial DNA searches by law enforcement agencies? What rules govern how genetic material can be used for tracking down criminals? What privacy rights are at risk? Whose DNA winds up in the database that police use to make the check?