Over the last decade, collecting DNA from people who are not charged with — or even suspected of — any particular crime has become an increasingly routine practice for police in smaller cities not only in Florida, but in Connecticut, Pennsylvania and North Carolina as well. While the largest cities typically operate public labs and feed DNA samples into the FBI’s national database, cities like Melbourne have assembled databases of their own, often in partnership with private labs that offer such fast, cheap testing that police can afford to amass DNA even to investigate minor crimes, from burglary to vandalism. And to compile samples for comparison, some jurisdictions also have quietly begun asking people to turn over DNA voluntarily during traffic stops, or even during what amount to chance encounters with police. In Melbourne, riding a bike at night without two functioning lights can lead to DNA swab — even if the rider is a minor.