Supreme Court justices are to meet privately Friday to weigh whether they will hear a major genetic-privacy case testing whether authorities may take DNA samples from anybody arrested for a serious crime.

The case has wide-ranging implications, as 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.

The issue confronts the government's interest in solving crime, balanced against the constitutional rights of those arrested to be free from government intrusion.

The case before the justices concerns a decision in April of Maryland's top court, which said it was a breach of the Fourth Amendment right against unreasonable search and seizure to take 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.

Maryland prosecutors argued that the mouth swab was no more intrusive than fingerprinting, (.pdf) 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.

In the justices' Friday conference, they are likely to agree to review the Maryland case, and announce their decision days later. That's because Chief Justice John Roberts has stayed the Maryland decision pending whether the justices review the case. In the process, he said there was a "fair prospect" (.pdf) the Supreme Court would reverse the decision. If the justices decline the case, the Maryland decision becomes law.

The National District Attorneys Association is urging the Supreme Court to overturn the Maryland decision, saying DNA sampling "serves an important public and governmental interest." (.pdf)

The group points to the Maryland case at hand, concerning defendant Alonzo King. After being arrested in 2009 on assault charges, a DNA sample he provided linked him to an unsolved 2003 rape case. He was later convicted of the sex crime, but the Maryland Court of Appeals reversed, saying his Fourth Amendment rights were breached.

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.

Still, the U.S. Supreme Court has held 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 with the right to draw blood from a suspected drunk driver without a warrant.

Maryland's law, requiring DNA samples for those arrested for burglary and crimes of violence, is not nearly as harsh as California's. The Golden State's statute is among the nation's strictest, requiring samples for any felony arrest.

A three-judge federal appeals panel has upheld California's law, although the court is reviewing the issue again with 11 judges.

DNA testing in the United States was first used to convict a suspected Florida rapist in 1987, and has been a routine tool to solve old or so-called cold cases. It has also exonerated convicts and those on death row.