Relative Doubt: Partial Match or “Familial” Searches of DNA Databases

In 2005, Denver District Attorney Mitchell Morrissey had DNA samples from three unsolved rape cases, but a search in the national DNA database had failed to turn up any matches. Typically, such a search looks for perfect identity between a crime-scene sample and a known offender using thirteen genetic markers. However, the software used for matching returns can return not only perfect matches, but also near or “partial” matches of fewer markers. Because genetic information is inherited, such partial matches may point toward a relative of the source, which in turn could lead to the perpetrator of the offense. In Morrissey’s cases, the search revealed several of these near-matches -one in each case, in fact. The only problem was that the matches came from the Oregon, Arizona, and California databases, and the national database stores entries anonymously, allowing each state to keep the identifying information of its offenders. Accordingly, Morrissey had to request the matching persons’ names from the federal government. And while federal rules did not prohibit a state from accessing information about its own offenders in such partial-match cases, they did not authorize the sharing of such information across jurisdictions. Thus, the head of the federal DNA database refused to disclose the names of the potential relatives. Frustrated by his inability to pursue the partial matches, Morrissey wrote to the director of the FBI laboratories, complaining that the policy “protects murderers and rapists.” Several days later, FBI Director Robert Mueller called Morrissey to discuss the issue. Shortly after that, Mueller ordered the adoption of an interim policy, which permitted states to decide for themselves whether to share the identities of persons in the database revealed in partial match searches. Arizona and Oregon then complied with Morrissey’s request, but California resisted. After a campaign by the state’s sheriff and district attorneys’ organizations, however, Attorney General Jerry Brown radically changed course. In April of 2008, Brown announced that California would not only share such information, but also laid out the first policy in the nation