The U.S. Supreme Court ruled on Monday that police can gather DNA samples, without a warrant, from suspects arrested in connection with serious crimes. In a 5-4 decision, the court ruled taking a mouth swab is only a minor intrusion and is reasonable under the Fourth Amendment. We asked law professor Daniel Medwed, an expert in criminal law and a leading scholar in the field of wrongful convictions, to analyze the significance of the ruling and its potential impact on future cases involving privacy and the Fourth Amendment.

What was your immediate reaction to the ruling?

I’m not surprised by the result. I suspected the court would extend the principle that you can be subjected to a cheek swab from after conviction to after arrest. But I was a little surprised by the court’s reasoning. The majority opinion focused on how the swab was comparable to the fingerprinting and photographing used in police booking procedures to identify subjects. However, the real reason this DNA is being collected is to put that information into a database to see if it helps solve a cold case or for use in future crimes. That is, it strikes me as odd that the decision didn’t directly address the key issue—that someone’s biological information could be used to tie that person to old crimes—but I think the identification argument is an easier one to make.

Frankly, I’m conflicted about this opinion. I’ve spent much of my career focused on the issue of wrongful convictions, and I’ve long viewed DNA as a tool to improve accuracy: to exonerate the innocent as well as fight crime and solve cold cases. But the privacy implications are somewhat troubling to many of us.

The Fourth Amendment and privacy seemed to be at the center of the dissenting justices’ argument. What’s your take on the impact of this ruling on these issues?

There are a few interesting privacy arguments here. Some argue that if a person hasn’t done anything wrong, there’s no downside of having his or her DNA in a database. But one privacy concern held by those suspicious of the government is the state’s ability to keep this information private so that it won’t be compromised, used, or sold for other purposes. Others might argue that this is a slippery slope. Does it give the state carte blanche to collect genetic information on citizens? The ruling doesn’t suggest a clear endpoint.

In February, Justice Samuel A. Alito Jr. described this as “the most important criminal procedure case that this court has heard in decades.” Now that the court has ruled, how would you measure its significance?

I do think it’s significant. First, the court has long wrestled with how to grapple with technology and the original intent of Fourth Amendment. How does the amendment’s language translate into the modern era with thermal imagery and GPS devices that allow for searches and seizures in ways the founding fathers never envisioned? It’s a fascinating wrinkle to this debate.

Secondly, I think it’s significant as a privacy interest case. It comes back to the extent to which someone’s genetic information may be stored, collected, and potentially used by the state—and what that means in this day and age with incredible advances in technology, medicine, and genetic testing. After all, data privacy and privacy of information in general is already under siege with sophisticated hackers.  On the one hand, the government is asking us to trust that it will only use this information for identification, and to some extent I think the ruling signals we should offer this trust. But what’s significant is that we just don’t know what the future holds.