BOB GARFIELD:  Consider this:  There you are, minding your own business when you get arrested, accused of some crime and – well, you know how it goes. You get read your Miranda rights and you’re taken to the police station, where they ask you a lot of questions, take your fingerprints to verify your identity and then they swab your cheek and collect a sample of your DNA. That last part, the DNA swab part, is a relatively new twist. Though it’s now a common practice in about half the states and on the federal level, it doesn't require anything more than your arrest. Well, that could soon change. On Tuesday of this week, the Supreme Court heard arguments about whether this practice is constitutional and what kind of privacy incursion routinely taking DNA might represent. Adam Liptak writes about the High Court for the New York Times. Adam, welcome back to the show.

ADAM LIPTAK:  Good to be here, Bob.

BOB GARFIELD:  Let's start with the case that was the center of discussion Tuesday. It concerned one Alonzo J. King.

ADAM LIPTAK:  Alonzo King is arrested for assault and they swab his cheek as part of the arrest process. It pops up in a database. He later was convicted of raping a 54-year-old woman. And the question in the case was whether that evidence should be suppressed because it may be that the Fourth Amendment says that swabbing his cheek was the sort of search that requires either a warrant or, at least, some level of individualized suspicion, and it's not clear you have that here, merely because you’re arrested for a wholly different crime.

BOB GARFIELD:  The central question is whether DNA collection is the equivalent of fingerprinting, which police have done for many decades, or whether it's something different.

ADAM LIPTAK:  Well, that’s exactly the right question because fingerprints, although not exclusively, are typically used to identify somebody, to tell you if you've got the right guy and maybe to tell you what that guy's been convicted of, what his rap sheet is. DNA, these days, is typically used not for identification purposes but to solve cold cases, to solve a case wholly different from that for which the person was arrested.

Now, the two things may be converging over time, and there was a lot of discussion at the argument saying, well, I understand today they’re different but two years from now, five years from now, we may have the ability to turn around the DNA evidence so quickly that you can use it for identification; you can use it to help a judge make a decision about whether to let somebody go on bail. So, one question for this Court is whether to spin this forward a couple of years out or whether to deal with the facts on the ground today.

BOB GARFIELD:  Yeah and, if you spin it more than a couple years out, it makes your head hurt because, while fingerprints don't have much more function than ID’ing someone's location at a crime scene, the DNA says so much more. It could tell the police, if they were interested, what diseases you have or will have. It can say something about future generations of your progeny. That's a lot of information to entrust to the cops?

ADAM LIPTAK:  Yeah, so the cops – you know, the Federal Government and the State of Maryland, said, we don't use it for that purpose. We only look at 16 markers on the - on the DNA, and that tells us nothing but, you know, who you are, a kind of barcode of your identification. And we’re not gonna look at that other stuff. You should please trust us. And I’m not sure the Supreme Court is necessarily ready to trust the government with such a trove of information about which most people probably think they have a reasonable expectation of privacy.

On the other hand, we do leave DNA behind all the time, so a question that a lawyer for Mr. King had a hard time with was, okay, what if we don't swab his cheek, what if we just offer him a root beer and when he leaves that behind, we swab that? Does he have a reasonable expectation of privacy in that can that he left behind?

BOB GARFIELD:  What was your sense of the Justices’ direction on this case?

ADAM LIPTAK:  It was really closely divided, and it didn't ideologically match up with some of what you might think. So when the lawyer for Maryland starts by saying, this really works great - we got 200 matches and 50 hits and we solved all these cold cases. Justice Scalia, typically conservative, says, well, that’s great. I bet all kinds of unreasonable searches would let you solve all kinds of crimes. So he seemed to be going in a pro-defendant direction. Justice Breyer, typically on the liberal side, seemed to think this was a very valuable tool and a fairly minor intrusion.

BOB GARFIELD:  I always do this to you, and I know it's unfair, but what's [LAUGHS] gonna happen?

ADAM LIPTAK:  It may well turn on the vote of Chief Justice Roberts, who said things pointing in both directions but did something unusual as the Court was agreeing to hear the case. He unilaterally stayed the decision of Maryland's highest court, which had suppressed the evidence, and said that Maryland could, in the meantime, while the Court hears arguments, go on and collect this kind of information. And, if I'm right, that he may be the decisive vote, he sort of tipped his hand that he may be okay with this kind of DNA collection.

BOB GARFIELD:  Adam, as always, thank you very much.

ADAM LIPTAK:  Great to be here.

BOB GARFIELD:  Adam Liptak covers the Supreme Court for the New York Times.