The following editorial appeared Thursday in the Los Angeles Times:

Identifying King Richard III's remains through DNA is just the latest reminder of the immense power of this evidence.

According to the Innocence Project, DNA evidence has helped exonerate more than 300 Americans convicted of crimes, including 18 who had served time on death row. Inversely, DNA evidence has been used to convict the guilty. The latter use of DNA information figures in a case to be argued before the Supreme Court this month.

Supported by virtually every other state, the Obama administration and local officials, the state of Maryland is seeking court approval for taking DNA samples from individuals arrested for serious crimes and checking that information against a database that includes evidence from unsolved crimes. The court should decline the request and affirm a ruling by Maryland's highest court that taking DNA samples from persons who haven't been convicted of a crime violates the Fourth Amendment's ban on illegal searches and seizures.

Several arguments for acquiring such information are being offered, including the compelling argument that it might implicate the suspect in another crime and help bring him to justice.

The problem is that the Fourth Amendment has traditionally required probable cause or at least reasonable suspicion before a search is conducted; the fact that someone has been arrested on suspicion of one crime doesn't create probable cause that he committed another. Unless he is convicted, he should have the same protection against unreasonable searches enjoyed by individuals who haven't been arrested. That may not be a popular conclusion, but it's the correct one.