The U.S. Supreme Court offered a surprising amount of concern Tuesday about states laws allowing police to collect a DNA sample of anyone arrested -- but not yet convicted -- of serious crimes.
A ruling soon on the privacy versus public safety question could have wide-reaching implications in the rapidly evolving technology surrounding criminal procedure.
Law enforcement lauds genetic testing's potential as the "gold standard" of reliable evidence gathering, especially to solve "cold cases" involving violent offenders.
But privacy rights groups counter the state's "trust us" promise not to abuse the technology does not ease their concerns that someone's biological makeup could soon be applied for a variety of non-criminal purposes.
The justices raised a host of hypotheticals in their spirited oral arguments, laying out two sharply divided scenarios.
"There is something inherently dangerous about DNA collection that is not the same as fingerprinting," said Justice Sonia Sotomayor. "How far do we let the state go each time it has some form of custody over you in schools, in workplaces, wherever else the state has control over your person?"
"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," said Justice Samuel Alito. "Why isn't this the fingerprinting of the 21st century? What is the difference?"
Twenty-six states and the federal government allow genetic swabs to be taken after a felony arrest and without a warrant.
Each has different procedures, but in all cases, only a profile is created. About 13 individual markers of some 3 billion are isolated from a suspect's DNA. That selective information does not reveal the full genetic makeup of a person, and officials stress, nothing is shared with any other public or private party, including any medical diagnostics.
The Obama administration has signaled its support.
The case involves a Maryland man convicted of a 2003 rape in Wicomico County in the state's Eastern Shore region. Alonzo King Jr. had been arrested four years ago on an unrelated assault charge, and a biological sample was automatically obtained at that time. That sample was linked to the earlier sexual assault.
King moved to suppress that evidence on Fourth Amendment grounds, but was ultimately convicted of the 2003 first-degree rape offense and was given a life sentence. Both King and his legal team turned down CNN's request for an interview.
A divided Maryland Court of Appeals later agreed with King, saying suspects under arrest enjoy a higher level of privacy than a convicted felon, outweighing the state's law enforcement interests. That court also said obtaining King's DNA immediately after arrest was not necessary in identifying him, and that the process was more personally invasive than standard fingerprinting.
The Fourth Amendment grants the "right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures."
The issue of citizen privacy has been particularly acute since the 9/11 attacks. Federal and state governments have stepped up surveillance of suspected terrorists and their allies and high-risk targets, like government buildings and shopping malls.
The current conservative majority court has generally been supportive of law enforcement in recent search and privacy disputes, but not always. The court last year ruled police could not place a GPS tracking device on a drug suspect's car for several weeks, without first obtaining a search warrant.
Chief Justice John Roberts last July allowed the Maryland DNA law to stay in effect until a full appeal could be filed. The high court then agree to decide the constitutional issues. Roberts at the time hinted his tentative support, but in arguments he was tough on both sides.
"There's no reason you couldn't undertake this procedure with respect to anybody pulled over for a [misdemeanor] traffic violation?" he asked with some concern, to state attorney Katherine Winfree. She said Maryland's law in three years produced 225 matches, 75 prosecutions and 42 convictions.
"Well that's really good," said Justice Antonin Scalia, somewhat facetiously. "I'll bet if you conduct a lot of unreasonable searches and seizures, you'd get more convictions, too. That [statistic] proves nothing."
Scalia said that catching bad guys is a "good thing, but the Fourth Amendment sometimes stands in the way."
Other members of the bench were equally skeptical.
Justice Ruth Bader Ginsburg: "This is very reliable tool, but it's not based on any kind of suspicion of the individual who's being subjected to it, right?"
Justice Elena Kagan: "Just because you've been arrested, doesn't mean that you lose the privacy expectations and things you have that aren't related to the offense that you've been arrested for. .. If it's just to solve cold cases, which is the way you started, then it's just like searching your house, to see what's in your house that could help to solve a cold case."
But there was a measure of support for the state's efforts.
Justice Stephen Breyer: "I can argue that it is certainly a much lesser intrusion than fingerprints. You have to stand there, have the thing rolled; stick out your tongue. I mean, it's hard to say it's more for me. Accuracy: it's much more accurate."