Nightly News   |  February 26, 2013

DNA evidence: Powerful tool or privacy violation?

The U.S. Supreme Court is examining whether or not the police can gather DNA profiles from people who have not been convicted of a crime in order to see if they might have convicted one. NBC’s Pete Williams reports.

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This content comes from Closed Captioning that was broadcast along with this program.

>>> now to what was described today by supreme court justice samuel alito as the most important criminal procedure case this court has taken on in decades. it involves the use of dna , which has become a powerful tool in criminal cases , both to find the guilty and to free the innocent. but the big question before the court, can the police gather dna samples from people who have not been convicted of any crime just to see if they might have committed a crime? a report tonight from our justice correspondent, pete williams .

>> reporter: it's a staple of police drama .

>> cold case in sacramento and new york. ran dna from rape kits ten years ago.

>> reporter: four years ago, maryland police took a dna sample from alonzo king when they arrested him on a gun charge, rubbing a cotton swab inside his cheek like this, then submitting his dna profile to a national database . it found a match with dna from an unsolved rape and robbery six years earlier. every state now gathers dna from anyone convicted of serious crimes. half the states do it with people arrested, too, but defense lawyers say that's just phishing with no grounds to think that some other crime was committed.

>> in the dna sample, there's a lot of medical information concerning the individual, about the individual's genetic heritage, about the people that they are related to.

>> reporter: but the mother of katie sepich, a college student raped and murdered in 2003 , says her daughter's killer could have been caught sooner if police had put his dna on file when he was arrested for an earlier crime.

>> we needed justice and we needed to know what happened, and we had to wait for an additional three years for that.

>> reporter: some justices today seem to side with the police. justice alito said dna taken from someone arrested is merely the fingerprint of the 21st century . justice breyer said dna is more accurate and it's less intrusive to swap a cheek than to roll all ten fingers for a set of prints. but others, including chief justice roberts asked, what are the limits? could you get dna from anybody pulled over for a traffic stop? and justice kagan asked, if police can use dna to check for past crimes, can the state go search your house, too? it's worth noting that all 50 states are in agreement about this case, and that's very unusual. they want the supreme court to uphold this expanded use of dna testing . they say, brian, that it helps solve crimes.

>> a whole new set of challenges since our framers set out to decide on our freedoms. pete williams , thanks, as always.