In my last blog post, I wrote about how reminding prisoners on their way out of prison that their DNA has been collected and stored in a database can reduce their future offending. However, the way that it’s actually been playing out in practice won’t deter people from committing crimes.
Simply informing convicted offenders that you have their DNA is insufficient to change their behavior. In order for their behavior to change, the convicted offender must be convinced that the collection and retention of their DNA evidence will increase (substantially) the likelihood that they will be caught for offending in the future.
And there’s the rub. While the United States is increasingly relying on DNA evidence to convict offenders who would otherwise go free, it doesn’t happen very often. And the reason why it doesn’t happen very often is that we are using DNA databases in an extremely inefficient way. We spend way too much money using DNA to aid investigations it mainly can’t help, and way too little solving crimes whose offenders can cause bigger social harms.
Prosecutors are especially motivated to use DNA in murder cases because of the crime’s seriousness. This is a very ineffective use of DNA testing because there is often no transfer of biological material from the assailant to the victim. A typical murder in the U.S. involves a firearm (about two-thirds of the time), and typically there is no physical interaction between the victim and the assailant. Other biological evidence left behind—DNA from a cigarette butt, hair in a hat—can link a person to a place, but doesn’t say anything about when they were at that place. None of this is to say DNA can never aid a homicide investigation, only that it is often a long shot.
DNA is much more efficacious in a burglary investigation—if investigators find your cigarette butt in a house right after it’s been burgled, you’re sunk. And our research at the Urban Institute finds that DNA test to be relatively inexpensive—as little as $3,500 to catch a felon.
And yet, we find that DNA evidence is about 10,000 times more likely to be processed from a homicide scene than from a residential burglary. Unfortunately, DNA testing resources are limited, and the focus on homicide crowds out testing DNA in burglary investigations.
While homicides cause many times more harm to society than burglary, it does not justify the lack of DNA processing of evidence from a burglary. For the disparity to be justified, the future harms prevented from solving a homicide would have to be 10,000 times greater than from solving a burglary.
They aren’t. They are in fact about the same. It turns out that burglary offenders nabbed by DNA average about three prior felony convictions, often for violent crimes. And they aren’t specialists—they rape, rob, and kill too. They are dangerous offenders who should be a much bigger priority for law enforcement and prosecutors.
And the link back to “we’ve got your DNA”? We’d nab more bad guys if we tested DNA from burglaries rather than murders, making the threat from DNA collection and retention much more real— and thus we would deter more future offending.
DNA illustration from Shutterstock.