The New York Times reports on a controversy brewing about genetics and the government. It reminds me of the film Gattaca with Ethan Hawke, Uma Thurman and Jude Law. “If you haven’t done anything wrong, you have nothing to fear,” a prosecutor in California said.

Law enforcement officials are vastly expanding their collection of DNA to include millions more people who have been arrested or detained but not yet convicted. The move, intended to help solve more crimes, is raising concerns about the privacy of petty offenders and people who are presumed innocent.

Until now, the federal government genetically tracked only convicts. But starting this month, the Federal Bureau of Investigation will join 15 states that collect DNA samples from those awaiting trial and will collect DNA from detained immigrants — the vanguard of a growing class of genetic registrants.

The F.B.I., with a DNA database of 6.7 million profiles, expects to accelerate its growth rate from 80,000 new entries a year to 1.2 million by 2012 — a 17-fold increase. F.B.I. officials say they expect DNA processing backlogs — which now stand at more than 500,000 cases — to increase.

Criminal justice experts cite Fourth Amendment privacy concerns and worry that the nation is becoming a genetic surveillance society.

DNA extraction upon arrest potentially erodes that argument, a recent Congressional study found. “Courts have not fully considered legal implications of recent extensions of DNA-collection to people whom the government has arrested but not tried or convicted,” the report said.

Minors are required to provide DNA samples in 35 states upon conviction, and in some states upon arrest.

Sixteen states now take DNA from some who have been found guilty of misdemeanors. As more police agencies take DNA for a greater variety of lesser and suspected crimes, civil rights advocates say the government’s power is becoming too broadly applied. “What we object to — and what the Constitution prohibits — is the indiscriminate taking of DNA for things like writing an insufficient funds check, shoplifting, drug convictions,” said Michael Risher, a lawyer for the American Civil Liberties Union.

This year, California began taking DNA upon arrest and expects to nearly double the growth rate of its database, to 390,000 profiles a year from 200,000.

Law enforcement officials say that DNA extraction upon arrest is no different than fingerprinting at routine bookings and that states purge profiles after people are cleared of suspicion. In practice, defense lawyers say this is a laborious process that often involves a court order. (The F.B.I. says it has never received a request to purge a profile from its database.)

When DNA is taken in error, expunging a profile can be just as difficult. In Pennsylvania, Ellyn Sapper, a Philadelphia public defender, has spent weeks trying to expunge the profile taken erroneously of a 14-year-old boy guilty of assault and bicycle theft. “I’m going to have to get a judge’s order to make sure that all references to his DNA are gone,” she said.

Mr. Morrissey pointed to Britain, which has fewer privacy protections than the United States and has been taking DNA upon arrest for years. It has a population of 61 million — and 4.5 million DNA profiles. “About 8 percent of the people commit about 70 percent of your crimes, so if you can get the majority of that community, you don’t have to do more than that,” he said.

In the United States, 8 percent of the population would be roughly 24 million people.

Britain may provide a window into America’s genetic surveillance future: As of March 2008, 857,000 people in the British database, or about one-fifth, have no current criminal record. In December, the European Court of Human Rights ruled that Britain violated international law by collecting DNA profiles from innocent people, including children as young as 10.

Critics are also disturbed by the demographics of DNA databases. Again Britain is instructive. According to a House of Commons report, 27 percent of black people and 42 percent of black males are genetically registered, compared with 6 percent of white people.

Rock Harmon, a former prosecutor for Alameda County, Calif., and an adviser to crime laboratories, said DNA demographics reflected the criminal population. Even if an innocent man’s DNA was included in a genetic database, he said, it would come to nothing without a crime scene sample to match it. “If you haven’t done anything wrong, you have nothing to fear,” he said.