The ruling did not fall along the court's ideological fault line. Conservative Justice Anton Scalia joined three liberals in dissent.
In the majority opinion, Justice Anthony Kennedy said when police officers make "an arrest supported by probable cause to hold for a serious offense and 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."
The Fourth Amendment bans unreasonable searches and seizures.
In 2003 a man concealing his face and armed with a gun broke into a woman's home in Salisbury, Md. He raped her, and the police were unable to identify him. They did take a sample of the invader's DNA from the woman.
In 2009 Alonzo King Jr. was arrested in Wicomico County, Md., and charged with first- and second-degree assault for menacing a group of people with a shotgun. "As part of a routine booking procedure for serious offenses, his DNA sample was taken by applying a cotton swab or filter paper -- known as a buccal swab -- to the inside of his cheeks. The DNA was found to match the DNA taken from the Salisbury rape victim."
King was convicted of the rape.
A Maryland appeals court set aside the conviction, finding that the state act authorizing DNA collection from felony arrestees was unconstitutional.
The U.S. Supreme Court reversed the state appeals court.
In dissent, Scalia said, "The Fourth Amendment forbids searching a person for evidence of a crime when there is no basis for believing the person is guilty of the crime or is in possession of incriminating evidence. That prohibition is categorical and without exception; it lies at the very heart of the Fourth Amendment."
He added, "The [majority's] assertion that DNA is being taken, not to solve crimes, but to identify those in the state's custody, taxes the credulity of the credulous."