The Case of the Bloody Brick In March 2003, a drunk in southern England threw a brick off a bridge late at night, striking and killing a truck driver traveling along the freeway below. Armed with DNA from the blood on the brick, the British police searched the United Kingdom's national DNA database, which includes convicted felons and people who have been arrested, but failed to get a direct match. They then conducted a DNA dragnet, asking hundreds of young men in the area to donate a sample voluntarily, but still came up short. Without any other leads, the police decided to conduct what's called a "familial search" of the national DNA database. They were looking not for perfect matches to convicted offenders but for near matches, in the hope of using them to identify a relative who might have committed the crime.
Ordinarily, when searching for actual offenders, the British police look for a perfect match to a DNA profile that contains 10 pairs of peaks, or "alleles," with one number in each pair provided by the father and the other by the mother. Only identical twins share genetic profiles on all 20 alleles, so if you get a perfect match between the DNA you find at the scene and the DNA database profile, you have very strong evidence that the person in the database committed the crime. But the police can also program the search to look for partial matches, identifying profiles that are similar but not identical to those in the database. A partial match can suggest that the person in the database didn't commit the crime, but a close relative whose DNA pattern varies slightly on some of the 20 alleles may have done so. Accordingly, the British authorities programmed the search to pull up any offender in the database who matched at least 11 alleles out of 20 from the blood on the brick.
Initially, this familial search produced more matches than the police could follow up. But then the authorities limited the search to young men from two counties near the crime scene. This narrowed the number of partial matches to around 25. After interviewing the person whose profile represented the closest match—16 out of 20 alleles—the police found he had a brother who lived in one of the nearby counties. They went to the brother, Craig Harman, who agreed to give a DNA sample. It turned out to match the DNA on the brick. Harmon confessed after being confronted with the match, and in 2004, he was convicted of manslaughter.
Two years later, the district attorney of Denver, Mitch Morrissey, learned about the trail from the blood on the brick to Craig Harman on a trip to the United Kingdom, where he met with officials from the home office, police, and Forensic Science Service. They praised the success of familial searches. According to the country's Forensic Science Service, the Brits have done 70 such searches since 2004, leading to 18 matches and 13 convictions. The success rate is estimated at around 10 percent, which seems low but which the police see as worthwhile.
Morrissey returned to the United Sates and pitched the FBI, urging the agency to expand the search capacity of its Combined DNA Index System for "familial searches." He met resistance from Thomas F. Callaghan, who was then head of the FBI laboratory's CODIS unit, which encompasses the national DNA database. Callaghan is a former forensic scientist with the Pennsylvania State Police who has a doctorate in molecular biology; he balked at Morrissey's suggestion. His concern was that if the FBI began doing familial searches without congressional or judicial authorization, there could be a political and legal backlash over privacy and civil liberties that would imperil the federal government's recent decision to begin storing DNA samples not merely from convicted felons but from anyone who is arrested.
Last March, at an FBI conference about genetic privacy, critics of familial searches made their case to the administrators of the national, state, and local DNA databases. Partly as a result, the FBI decided not to reconfigure the national CODIS software to allow familial searches. Nevertheless, current FBI policy allows individual states to decide whether to proceed with familial searches on their own. As a result, last April, California Attorney General Jerry Brown (who is considering a run for governor) began to allow familial DNA searching in the largest state database in the country. The decision may provoke precisely the legal and political backlash that Callaghan predicted.
The California DNA database now contains approximately 1.2 million convicted people. And it's about to grow dramatically. In January, Brown announced a "major expansion" of the California database, as the state began to add the DNA of arrestees. California expects this to increase the pool of new DNA profiles from 200,000 to nearly 390,000 a year.
All of this could mean a slew of legal challenges on the horizon—not only over familial searching but also over the decision to include people who have been arrested in DNA databases at all, as 14 states and the federal government have done. In December, the European Court of Human Rights held that Britain's decision to store the DNA of unconvicted people violates European privacy guarantees—throwing the future of the British database into question.
The legal limits on family searches and DNA databases are murky, but the political implications are explosive for one big reason in particular: race. African-Americans, by several estimates, represent about 13 percent of the U.S. population but 40 percent of the people convicted of felonies every year. The CODIS database of 6.6 million now includes samples from convicted offenders. As arrestees are added to this mix, CODIS may soon grow to 50 million samples, which might be even more disproportionately African-American. Hank Greely of Stanford Law School has estimated that 17 percent of African-American citizens could be identified through familial searches, as opposed to only 4 percent of the Caucasian population. Once the implications of the racial disparity become clear, there may be a reaction against ever-more-expansive forms of DNA collection that makes the debate about racial profiling look tame.
The Dilemma of "CODIS Creep"
Not long ago, I drove to Quantico, Va., to meet with Tom Callaghan, who recently left CODIS, and to tour the CODIS unit, located on a bucolic Marine base in the gleaming new FBI Laboratory on Investigation Parkway. As we sat around a conference table, Callaghan gave me a history of CODIS, which contains national, state, and local DNA databases of convicted offenders, arrestees, crime scenes, and missing persons. The story he told was one of steady expansion. States began to set up their own databases in the early 1990s, and in 1994 Congress authorized the creation of the National DNS Index System. It launched in 1998 and originally included only nine states. Federal offenders were added two years later. In the beginning, only violent felons went into the federal database; that later expanded to all felons and then to all felony arrestees. Today, the national database includes 178 labs, and the CODIS software is distributed to all 50 states and 44 labs in 30 foreign countries.
Flipping through his PowerPoint slides, Callaghan explained to me how CODIS works. Each CODIS profile contains 52 characters representing 13 genetic locations, with two results per location and two digits for each result. Every Monday at 9 a.m., the national database automatically conducts two searches, looking for matches between the DNA of convicted offenders and the DNA at crime scenes. The automatic search also compares all crime-scene DNA samples with one another in search of serial criminals. A request for a specific search—say, from Florida to search the national database for a serial killer at large—goes to the custodian of the national database. As of January, the FBI claims that CODIS searches have "aided" more than 83,000 investigations. In addition, state investigators have provided names for state investigations more than 60,000 times, and states have traded the names of offenders 8,818 times. Still, the feds don't keep statistics on how many of these "cold hits" have actually led to convictions.