Civil liberties groups worry inadequate testing by overwhelmed lab technicians can lead to errors, such as the one that sent Dwayne Jackson to prison for armed robbery. It was three years before a lab mistake was noticed, and the Nevada man was freed as an innocent man.

DNA -- Deoxyribonucleic acid -- is a coded molecule providing a genetic map for the development of all known living organisms. By 2000, all 50 states and the federal government required DNA collection from convicted offenders, and that was soon expanded by many jurisdiction to criminal arrests.

The number of offender profiles in federal Combined DNA Index System is now about 10 million, with more than a million arrestee profiles.

Congress in December passed the Katie Sepich Enhanced DNA Collection Act, a grant program to help states pay for the expanded system. The 22-year-old woman was murdered in 2003, but her killer was not identified until three years later, after his conviction for another crime, when his DNA matched cold-case evidence found under the victim's fingernails.

Her mother, Jayann Sepich, personally lobbied lawmakers for months to ensure passage.

"This is what I expected," Sepich said. "And from the very beginning I knew this would end up in the Supreme Court. I knew we would have to have a ruling and I had faith that it would be a good ruling.  And it is a very good ruling," she said.

President Barack Obama signed the bill earlier this year. "It's the right thing to do," he said in 2010, of expanding DNA swabs for arrestees. "This is where the national registry becomes so important."

The case is Maryland v. King (12-207).