Police used portable fingerprint machines more than 1,600 times last year, raising questions about how they're used and whether the results are stored when there's no arrest. The New York Civil Liberties Union wants to know how many of the 1,612 sets of prints were taken during stop-and-frisk encounters. And it's worried that fingerprints taken from people who aren't charged with a crime could end up in an NYPD database. "We are concerned about fingerprints being taken from people caught in coercive stops and frisks, and about the NYPD using these machines as a backdoor way to build a print database of innocent people," said Christopher Dunn, the group's associate legal director. "To do so would be wrong and illegal."