DNA evidence was undeniably the key to the arrest and charging of Lonnie David Franklin Jr., believed to be the Grim Sleeper responsible for a string of slayings in Los Angeles between 1985 and 2007. Many will cite this use of DNA evidence in a high-profile serial murder case as one more reason to increase reliance on this important investigative tool. But in fact it's precisely at a moment like this when an investigative triumph can blind us to the dangers of expanding genetic surveillance.
There were actually three different uses of DNA evidence in the Grim Sleeper investigation that we should be concerned about. They all turn basic assumptions about our criminal justice system on their heads. The first is the use of familial DNA searches. Most of the time, investigators search state DNA databases to find a complete match linking a particular person's DNA profile to crime scene evidence. Familial matches are different. A "hit" in the database establishes definitively that the person in the database is not the wanted suspect, but suggests that it is one of his or her relatives.
Why is this problematic? Keep in mind that in usual police "searches," there must be individualized probable cause for suspicion, as required by the 4th Amendment. With familial searches, the only reason the police identify their suspect is because he is genetically related to someone in a DNA database. If that sounds like guilt by association, it is. Why should the mere inclusion of one of your family members in a DNA database mean that you might be a target of an investigation one day?
The second investigative technique used in the Grim Sleeper investigation was the use of "abandoned" or "discarded" DNA. We all leave DNA on used coffee cups, smoked cigarettes and many other items on a daily basis. After the police turned their focus to Franklin, undercover police followed him until he left some of his DNA on a piece of pizza as well as silverware and a glass after a meal out.
Few rules govern the circumstances in which police can collect this involuntarily shed DNA. Police typically defend the practice by saying it produces results. Of course, when successful matches are found, the unrestrained collection of abandoned DNA sounds defensible. But what about all of the hunches that police might like to pursue in this way? Have we all silently consented to giving up our discarded DNA to the police?
The third use of DNA in the investigation is unlikely to receive much fanfare; it wasn't successful. Yet it is equally dangerous to civil liberties. Two years ago, LAPD vice officers arrested a number of suspected johns not as part of a crackdown on prostitution but rather for the purpose of collecting their DNA. (Many of the Grim Sleeper's victims were prostitutes.) Such a technique is known as a DNA dragnet. As of January 2009, Proposition 69 allows the state to collect DNA not just from those convicted of felonies but also from all people who have simply been arrested on suspicion of committing felonies. Atty. Gen. Jerry Brown's formal approval of familial searches is still limited to searching profiles of convicted felons in special cases, but it's not hard to imagine an expansion to all cases regardless of severity, and to arrestee profiles as well.
There's no doubt that DNA evidence gives the police an important tool. Without it, the Grim Sleeper case would probably be yet another unsolved case. The trouble is that we are rushing forward with these uses of DNA evidence with little consideration of the ever-increasing scope of genetic surveillance over our citizens. Many states that have not formalized their policies in these areas have taken note of what the police did in this case. What matters isn't just that this particular fish was caught; it's the ever-widening net over us.
Elizabeth Joh, a professor at the UC Davis School of Law, has written widely about DNA evidence, undercover policing and police privatization.