The department said it is also going to streamline the process for people seeking to have their DNA removed from the index. Those who have been acquitted of crimes, for instance, would only have to provide a document showing that they were found not guilty. Before, they were required to get a court order, which is no easy task, Mr. Barrows said.

The new rules, first reported in The Wall Street Journal, also place curbs on the collection of DNA from teenagers and children. Investigators will only be able to collect DNA from juveniles in connection with felonies, sex crimes, firearm crimes or hate crimes, not misdemeanors. And they will not only have to get the consent of the minor, but they also must notify parents or guardians, who can object to it.

In the past, Mr. Barrows said, investigators were not required to obtain permission from a minor or guardian before walking away with a piece of DNA evidence.

A growing number of law enforcement agencies throughout the country — including police departments in Connecticut, California and Maryland — have amassed genetic databases that operate by their own rules, outside of state and federal guidelines, which tend to be far more strict.

Those databases have become the center of a debate over how to strike a balance between civil rights and crime-fighting, as DNA has become an increasingly common tool in investigations and prosecutions.

New York State law requires a conviction before someone’s DNA can be included in the state-operated DNA databank. But databases built by local authorities are not subject to the state rules.

Announcing the changes for obtaining and storing DNA samples, Commissioner Shea said he hopes to build trust with New Yorkers while still continuing to collect evidence in ongoing criminal investigations.