DNA evidence has been revolutionary in the criminal justice system. It has led to the solving of cases that otherwise would never have been solved. It has also pointed out shortcomings in the criminal justice system when it has been used to exonerate the wrongly convicted. The New York Times had a story about an effort in the State of New York to expand the collection of DNA from nearly everyone arrested, even those arrested only for minor crimes.
“Every single time we’ve expanded the DNA database, we have shown how effective it is in convicting people who commit crimes, and we’ve also shown that it can be used to exonerate the innocent,” said Richard M. Aborn, the president of the Citizens Crime Commission.
The last system to identify criminals was fingerprint evidence. It has been standard procedure for decades to collect rolled ink prints on a ten print card (or the digital equivalent thereof) every time a person is arrested. These prints are collected even if it's from a person only arrested for a minor offense.
Up until now, most states only collect DNA samples from persons arrested for felony grade offenses or a few select other crimes. New York's effort is likely just the first of many states that are going to expand the collection and make it as ubiquitous as the collection of fingerprints.
This is a very good thing.