Should the police be allowed to warrantlessly collect and index the DNA of people merely arrested for a crime, while they are still cloaked in the presumption of innocence and have not been found guilty of anything? Over and over again, we've warned courts throughout the country the answer is no, and it now looks like judges are taking notice, including the U.S. Supreme Court.

Courts and judges throughout the country have been split over the controversial practice of warrantless DNA collection from mere arrestees. The samples collected by state and federal law enforcement officials are placed into CODIS, a federal DNA database that law enforcement officers throughout the country are permitted to access.

In California, federal and state courts have reached different conclusions on the constitutionality of Proposition 69, California's DNA collection scheme. The California Court of Appeal (PDF) initially found the practice unconstitutional as a violation of the Fourth Amendment's right to be free from unreasonable searches and seizures. That decision is now on review to the California Supreme Court. Meanwhile, a federal three judge panel of the Ninth Circuit Court of Appeals (PDF) rejected a lawsuit brought by the ACLU of Northern California and instead found Prop. 69 constitutional.

Similarly, the Third Circuit Court of Appeals (PDF) found the practice constitutional in a case out of Pennsylvania, while the Maryland Court of Appeal (PDF) found the warrantless DNA collection of mere arrestees to be unconstitutional. It's telling that many of these decisions highlight deep divisions within the bench, spurring impassioned dissenting opinions.

This division is finally working its way to the highest courts of the country. First, the entire Ninth Circuit Court of Appeals last week agreed to rehear (PDF) its opinion dismissing the ACLU challenge to Prop. 69. Then on Monday, Chief Justice Roberts of the U.S. Supreme Court signalled there is a "reasonable probability" that the high court would step in to review the conflicting opinions. His comments came in a brief order (PDF), granting the state of Maryland's request to stay the decision finding warrantless DNA collection from mere arrestees to be unconstitutional.

If and when the the Supreme Court reviews this issue, it needs to be cognizant of the enormous privacy concerns surrounding the collection and storage of DNA in a federal database. DNA is the most intimate and sensitive aspect of a human, able to reveal a snapshot of a person -- and their family's -- medical and genetic history. The history of CODIS and its continued expansion shows that Ninth Circuit Chief Judge Kozinski (PDF) was right in warning that the "voracious appetite of law enforcement" needed to be curbed by the courts. What initially started as DNA collection of individuals convicted of violent felonies has expanded to include all felons and now covers individuals not even convicted. And as we explain in detail in a recently published whitepaper, DNA collection is now a routine part of the immigration system, where individuals are not under arrest, let alone suspected of committing any crimes.

Chief Justice Roberts' brief order suggests he may not be sympathetic to the privacy issues at stake. But the pro-privacy concurring opinions of Justices Sotomayor and Alito in another recent Fourth Amendment case -- United States v. Jones -- suggests there are some on the Supreme Court who recognize we live in an age where technology has the serious potential of shrinking privacy. And that means courts must recognize that giving DNA Fourth Amendment protection is essential in order to keep sensitive biometric data from prying government eyes.