Investigators whose ability to crack down on "virtual" child porn was limited by the courts have turned to a network of computer databases to prove that kids depicted in online images actually exist. Using programs that compare digital pictures like an analyst compares fingerprints, agents are able to automatically scan images seized from suspects and see whether the same photograph has turned up in a previous investigation.
Once a match is found, the agents can see whether the child in the photograph has ever been identified by law enforcement groups around the globe.

The effort has taken on extra import since April, when the Supreme Court voided a law making it a crime to depict children in sexual situations, even if the models used were actually over 18 or the pictures were realistic fakes.

While the decision hasn't crippled anti-child-porn efforts, it has led agents to put new emphasis on proving that pictures traded online contain real victims, said Michelle Collins, of the National Center for Missing and Exploited Children.

"There is more of a need for law enforcement and prosecution teams to have their images reviewed," she said. "They want to be able to go into court and tell a jury, 'This is no fake.'"

The Justice Department said it is overseeing efforts to centralize what is now a network of independent systems operated by several law enforcement agencies into a new, highly advanced system developed by U.S. Customs agents.

Investigators in several countries have contributed pictures to the system, as have the FBI, Secret Service, Postal Inspection Service and exploited-children groups.

The computer system has been in development since 1999, but only began to be deployed in January, said Mike Netherland, acting director of the Customs bureau's cyber-smuggling center. It is expected to be fully activated within 90 days, he said, and eventually include most of the illicit photographs in circulation on the Internet.

The system could prove especially valuable to smaller police departments that don't have the manpower to identify victimized children on their own.

"If you are a local law enforcement officer in the middle of Iowa, and you haven't had a lot of child pornography cases, how would you know whether the children in these photographs are from your home town, or another country?" Collins said.

"But with these systems, and with the international cooperation we've been getting, it doesn't matter where a child lives. It could be anywhere, and if that child has previously been identified, we can make a match."

In a case this year in Philadelphia, investigators were able to trace the victims in two photographs sent by e-mail from a high school teacher to an FBI agent posing as a 12-year-old girl.

One was an American girl whose abuser had previously been indicted and fled the country. The other was a girl from Manchester, England, whose stepfather was convicted of abuse sentenced to 12 1/2 years in prison in 1998.

The teacher, Robert Lester, pleaded guilty on March 3.

In its ruling on the Child Pornography Prevention Act last year, the Supreme Court sided with critics who said that the nation's ban on material that "appears to be" a child would outlaw mainstream works like "Lolita" and "Romeo and Juliet," both of which feature minors engaged in sex.