In April 2009, police easily arrested Alonzo J. King Jr. in Wicomico County, Md. After King pointed a shotgun at a group of people, one of them told the police who did it, and King readily admitted his guilt. He ended up pleading guilty to a misdemeanor.
This case is now before the Supreme Court because of what the authorities did next. When King was arrested, police took a swab from inside his cheek for DNA testing. They did not need his DNA to link him to the shotgun incident. Instead, the police entered Kings DNA profile into both the Maryland and the FBIs databases. Kings profile was then automatically compared every week to evidence from all unsolved crimes. And, in fact, Kings DNA matched DNA from an unsolved sexual assault case, for which he was later convicted and sentenced to life in prison.
If Maryland had required King to submit his DNA once he was convicted, there would be no Supreme Court challenge. Maryland vs. King is about something new: More than half of the 50 states and the federal government authorize compulsory collection of DNA from people who have been arrested. But the Supreme Court has never held that police can also search a suspect for evidence of past or future crimes. Marylands justification for this unprecedented expansion of police power? Bigger is better. Add arrestee profiles to the database, and more crimes will be solved.
Wrong. Research shows that bigger is only better if DNA databases grow in the right way: by entering more samples from crime scenes, not samples from arrestees. DNA databases already include 10 million-plus known offender profiles. But a database with every offender cannot solve a crime if no physical evidence was collected or tested.
Police routinely collect physical evidence in homicides and most rapes. But evidence is not collected from eight out of 10 crime scenes for other serious offenses. Many jurisdictions do not even have dedicated and trained crime scene investigators.
States such as California, which vastly expanded DNA databanks to include arrestees, do not generate dramatically more matches between offenders and crime scenes than do states with much smaller databases, such as New York or Illinois. That is because New York and Illinois enter crime scene samples at rates comparable to California. The lesson is clear: Police solve more crimes not by taking DNA from suspects who have never been convicted, but by collecting more evidence at crime scenes.
Even worse, taking DNA from a lot of arrestees slows the testing in active criminal investigations. After all, 12 million or more people are arrested each year. Backlogs created by arrestee DNA sampling mean that rape kits and samples from convicted offenders sit in storage or go untested. This hurts innocent suspects. And although you likely have a right to have your DNA expunged if your arrest was mistaken, in some states it is up to you to petition the court.
Putting DNA from arrestees into databanks also exposes more innocent people to the risk of false accusation or conviction. Interpretation of DNA evidence from known offenders is straightforward, but crime scene samples often require subjective judgments that may lead to errors. What is more, cross-contamination and accidental sample switches have occurred in labs across the country. Improvement seems less likely if crime labs are inundated with DNA from arrestees. The FBI has also opposed confidential access for researchers who could independently assess government assertions about the accuracy of DNA databases.
In addition, arrestee testing exacerbates the racial disparities in DNA databases. Because blacks and Hispanics make up a disproportionate share of convicts, they are overrepresented in databases. Racial disparities in arrest rates can be even starker. Allowing states to bank DNA of arrestees will mean including disproportionate amounts of genetic information from blacks and Hispanics as compared to other groups.
Kings case may seem like a poster-child for DNA database expansion because his sample closed a serious unsolved case. But King had at least six prior convictions at the time of his sentencing for the shotgun offense. A state law limited to taking DNA from convicted offenders could have authorized his testing. The same is true of dozens of other arrestee DNA success stories.
That suggests that the line between arrest and conviction is the right place to locate the constitutional limit on the governments unending appetite for collecting our DNA. If the Supreme Court approves Marylands law, then DNA samples will be routinely taken from people upon arrest just like fingerprints. Unlike fingerprints, however, the DNA samples will be used not to identify people, but to forever implicate them as one of the usual suspects. Also unlike fingerprints, DNA samples convey a lot of information. Some states have even decided, without judicial approval or new laws, to use DNA databases to find not only people in the database, but also their family members. And as technology evolves, who knows what is next? What we know now is that no good evidence shows that taking from DNA from arrestees helps to solve crimes in any meaningful way. We also know the cost to liberty and privacy. Thats the tradeoff the Supreme Court should weigh.