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On July 7, 2010, Los Angeles police announced the arrest of a suspect in the Grim Sleeper murders, so called because of a decade-long hiatus in killings. The break in the case came when California searched its state DNA database for a genetic profile similar, but not identical, to the killer’s. DNA is inherited in specific and predictable ways, so a source-excluding partial match might indicate that a close genetic relative of the matching offender was the Grim Sleeper. California’s apparent success in this case has intensified interest in policymaking for source-excluding partial matching. To date, however, little information about existing state policies, and the wisdom of those policies, has been available. This Article reports the results of a survey of state policies governing source-excluding partial matching — the most complete survey of its kind. The Article also dismantles a distinction drawn by more than a dozen states between partial matches that arise fortuitously during the course of routine database searches and partial matches that are deliberately sought, exposing this distinction as harmful and illogical. In examining this feature of state policies, this Article is immediately relevant to determining how states ought to address the ever-expanding scope of uses to which DNA databases may be put.