DNA and the Constitution

On Tuesday, the Supreme Court is scheduled to hear argument about whether it is constitutional for a state to collect DNA from people charged with violent crimes but not yet convicted. Last April, the Maryland Court of Appeals ruled that a state law authorizing such collection violated the Fourth Amendment’s prohibition against unreasonable searches and seizures.

Maryland law enforcement officials were allowed to continue collecting DNA samples, however, through an order last July by Chief Justice John Roberts Jr. He said there was a “fair prospect” that the Supreme Court would reverse the Maryland decision, which conflicts with rulings of the Virginia Supreme Court and of the United States Courts of Appeals for the Third and the Ninth Circuits on similar statutes in other states. But the justices should uphold the Maryland court’s ruling, thus calling into question those other rulings. The Maryland law clearly contravenes the Fourth Amendment.

The case involves the collection of DNA from Alonzo Jay King Jr. after his arrest on assault charges in 2009. His DNA profile matched evidence from a rape in 2003, and...