In an opinion delivered by Justice Kennedy today the Supreme Court said that taking a DNA sample from a suspect is the same as fingerprinting someone upon arrest, and that the purpose is indentification of the suspect.
“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," said Justice Kennedy.
"That assertion taxes the credulity of the credulous," said Justice Scalia in a dissent delivered from the bench. "In approving that suspicionless search, the Court has cast aside a bedrock rule of our Fourth Amendment ..."
The case is Maryland v. King