The Supreme Court on Friday agreed to review a major genetic-privacy case on whether authorities may take DNA samples from anybody arrested for serious crimes.

The case has wide-ranging implications, because at least 21 states and the federal government have regulations requiring suspects to give a DNA sample upon arrest. In all the states with such laws, DNA saliva samples are cataloged in state and federal crime-fighting databases.

Without comment, the justices opted to take on an April decision (.pdf) from Maryland’s top court, which said it was a breach of the Fourth Amendment right against unreasonable search and seizure to take, without warrants, DNA samples from suspects who have not been convicted.

The Maryland Court of Appeals, that state's highest court, said that arrestees have a "weighty and reasonable expectation of privacy against warrantless, suspicionless searches" and that expectation is not outweighed by the state’s "purported interest in assuring proper identification" of a suspect.

The case involves Alonzo King, who was arrested in 2009 on assault charges. A DNA sample he provided linked him to an unsolved 2003 rape case, and he was later convicted of the sex crime. But the Maryland Court of Appeals reversed, saying his Fourth Amendment rights were breached.

Maryland prosecutors argued that mouth swabs were no more intrusive than fingerprinting, but the state's high court said that it "could not turn a blind eye" to what it called a "vast genetic treasure map" that exists in the DNA samples retained by the state.

The court was noting that DNA sampling is much different from compulsory fingerprinting. A fingerprint, for example, reveals nothing more than a person’s identity. But much more can be learned from a DNA sample, which codes a person’s family ties, some health risks and, according to some, can predict a propensity for violence.

The issue before the justices does not contest the long-held practice of taking DNA samples from convicts. The courts have already upheld DNA sampling of convicted felons, based on the theory that those who are convicted of crimes have fewer privacy rights.

But the U.S. Supreme Court has previously ruled that when conducting intrusions of the body during an investigation, the police need so-called "exigent circumstances" or a warrant. For example, the fact that alcohol evaporates in the body is an exigent circumstance that provides authorities the right to draw blood from a suspected drunk driver without a warrant.

The justices are to hear the Maryland case in the coming months.