WASHINGTON — The Supreme Court struggled on Tuesday with what one of the justices called its most important criminal procedure case in decades, whether to let police take DNA without a warrant from those arrested in hopes of using it to solve old cases.
Justices seemed conflicted over whether police have a right to take genetic information from people who have only been arrested without getting a judge’s approval first, or if the government’s interest in solving cold cases trumped the immediate privacy rights of those under police suspicion of other crimes.
One justice seemed to make clear what he thought. ‘‘I think this is perhaps the most important criminal procedure case that this court has heard in decades,’’ said Justice Samuel Alito, a former prosecutor.
‘‘This is what is at stake: Lots of murders, lots of rapes, that can be solved using this new technology that involves a very minimal intrusion on personal privacy,’’ Alito said later. ‘‘Why isn’t this the fingerprinting of the 21st century? What is the difference? If it was permissible, and it’s been assumed to be so for decades, that it is permissible to fingerprint anybody who’s booked, why is it not permissible to take a DNA sample from anybody who is arrested?’’
But Chief Justice John Roberts and Justice Elena Kagan questioned how far the government can go if they decide that the police have an interest in people’s DNA to help solve cases, with Roberts noting that it would not take much for police to add DNA swabs to traffic stops. ‘‘Police officers who give Breathalyzer tests, they can also take a Q-tip or whatever and get a DNA sample, right?’’ Roberts said.
‘‘It could be any arrestee, no matter how minor the offense,’’ Kagan said. ‘‘It could be just any old person in the street. Why don’t we do this for everybody who comes in for a driver’s license because it’s very effective?’’
Getting DNA swabs from criminals is common. All 50 states and the federal government take cheek swabs from convicted criminals to check against federal and state databanks, with the court’s blessing.
But now 28 states and the federal government also take samples from people who have been arrested for various crimes, long before their guilt or innocence has been proven.
According to court documents, the FBI’s Combined DNA Index System or CODIS — a coordinated system of federal, state, and local databases of DNA profiles — contains more than 10 million criminal profiles and 1.1 million profiles of those arrested.
In the case before the court, a 53-year-old woman was raped and robbed but no one was arrested. Almost six years later, Alonzo King was arrested and charged with felony second-degree assault.
Taking advantage of a Maryland law that allowed warrantless DNA tests following some felony arrests, police took a cheek swab of King’s DNA, which matched a sample from the 2003 Salisbury rape. King was convicted of rape and sentenced to life in prison.
King eventually pleaded guilty to a lesser charge of misdemeanor assault from his arrest, a crime for which Maryland cannot take warrantless DNA samples. The state courts said it violated King’s rights for the state to take his DNA based on an arrest alone.
The state Court of Appeals said King had ‘‘a sufficiently weighty and reasonable expectation of privacy against warrantless, suspicionless searches.’’
The Supreme Court is reviewing that decision. The justices will make a decision later this year.
Almost all the justices participated in the spirited back-and-forth with lawyers Tuesday — Justice Clarence Thomas did not say anything, as is his custom.
A decision may not fall along the court’s ideological lines — for example, conservative Justice Antonin Scalia seemed at times to concern himself about the program’s reach, and the usually liberal-voting Justice Stephen Breyer seemed to think that DNA cheek swabs were no more intrusive than fingerprinting, a position expected more from the court’s conservative wing.