In a 5-4 decision on Monday, the Supreme Court of the United States ruled (PDF) that the government has the right to collect a DNA sample from anyone arrested and charged for a “serious crime” without a warrant and well before a conviction.

“When officers make an arrest supported by probable cause to hold for a serious offense and they bring the suspect to the station to be detained in custody, taking and analyzing a cheek swab of the arrestee’s DNA is, like fingerprinting and photographing, a legitimate police booking procedure that is reasonable under the Fourth Amendment,” wrote Justice Anthony Kennedy in the majority opinion.

The case involves a 2003 incident in Salisbury, Maryland where a man broke into a woman’s home and raped her. The police were unable to identify or catch any suspect, but they did obtain a sample of his DNA.

Six years later, Alonzo King was arrested in Wicomico County, a southeastern region of Maryland, on separate charges of first- and second-degree assault. The arrest followed accusations against King for menacing people with a shotgun. When he was booked for the assault, police took a DNA sample via a buccal swab from the inside of his cheeks. The police found that his DNA matched the 2003 rape case, and King was subsequently tried and convicted for the rape charge.

King appealed to the Courts of Appeals of Maryland, which found that the original cheek swab constituted an unreasonable search and overturned his conviction. The state prosecutor appealed, sending the case to the Supreme Court.

In the majority opinion, Justice Anthony Kennedy wrote, “The legitimate government interest served by the Mary­land DNA Collection Act is one that is well established: the need for law enforcement officers in a safe and accu­rate way to process and identify the persons and posses­sions they must take into custody.”

He added:

The task of identification necessarily entails searching public and police records based on the identifying infor­mation provided by the arrestee to see what is already known about him. The DNA collected from arrestees is an irrefutable identification of the person from whom it was taken. Like a fingerprint, the 13 CODIS loci are not themselves evidence of any particular crime, in the way that a drug test can by itself be evidence of illegal narcot­ics use. A DNA profile is useful to the police because it gives them a form of identification to search the records already in their valid possession. In this respect, the use of DNA for identification is no different than matching an arrestee’s face to a wanted poster of a previously unidentified suspect; or matching tattoos to known gang symbols to reveal a criminal affiliation; or matching the arrestee’s fingerprints to those recovered from a crime scene.

In an attempt to head off worries about law enforcement collecting DNA samples willy-nilly, Kennedy wrote, "If in the future police analyze samples to determine, for instance, an arrestee’s predisposition for a particular disease or other hereditary factors not relevant to identity, that case would present additional privacy concerns not present here.”

Meanwhile, in the dissenting opinion, Justice Antonin Scalia countered strongly: