Now there’s DNA sampling. Obama told [America's Most Wanted host John] Walsh he supported the federal government, as well as the 18 states that have varying laws requiring compulsory DNA sampling of individuals upon an arrest for crimes ranging from misdemeanors to felonies. The data is lodged in state and federal databases, and has fostered as many as 200 arrests nationwide, Walsh said.The American Civil Liberties Union claims DNA sampling is different from mandatory, upon-arrest fingerprinting that has been standard practice in the United States for decades.A fingerprint, the group says, reveals nothing more than a person’s identity. But much can be learned from a DNA sample, which codes a person’s family ties, some health risks, and, according to some, can predict a propensity for violence.
Note that this is upon arrest, not upon conviction. Setting aside for a moment the question of civil liberties, this would be a hideously expensive proposition. As noted over at Ace's place, there are around 38,000 arrests per day nationwide not counting traffic violations, so this would require massive infrastructure.