More federal judges are showing leniency toward individuals who view child pornography but who aren't themselves molesters, according to recent data on prison sentences.

Judges are looking skeptically at prosecutors' requests to give 15- to 25-year sentences for viewing sexual images of minors, handing down more sentences of five to 10 years, or in some cases probation. The movement has been gaining steam over the past two years even as the Justice Department has made child pornography and other child-exploitation prosecutions a top priority, leading to more than 2,300 cases last year, the highest figure since the department began tracking the statistic.

"We've reached a critical momentum for change," said Troy Stabenow, a federal public defender in Missouri whose critique of child-pornography sentences has been cited by judges. "The recent sentences are signaling, as strongly as I have ever seen, that judges around the country think the current system is broken."

For years, federal sentencing guidelines have provided that someone convicted of downloading child porn would receive a minimum of five years in prison, plus extra time for, among other things, using a computer or having more than 10 images. Judges were rarely able to deviate from the guidelines. But Supreme Court rulings in 2005 and 2007 effectively made the guidelines advisory, not mandatory. Now, judges increasingly are giving prison terms for child porn that are lower than the range recommended by the guidelines.

In the 12 months ended September 2009, federal judges gave prison sentences below the guidelines in 44% of cases in which individuals obtained child pornography or shared it with others, up from 27.2% two years earlier, according to data from the U.S. Sentencing Commission, a federal agency that develops the guidelines. Those figures exclude cases in which judges gave lighter sentences at the prosecutors' request. In the same two-year period, the rate by which judges gave below-guideline sentences for all criminal cases rose to 16.9% from 12.5%.

Some judges who criticize the recommended sentences say they are the result of an unfair linking of child-porn users and sexual predators. While some child-porn viewers are accused or convicted of physical molestation, psychologists who treat sexual deviants say it is unclear whether most viewers of child pornography are likely to commit such acts. Many of the defendants convicted of downloading images said they would never molest a child.

The shift has upset advocates of abused children who say the sentences won't deter future misconduct. "There's a clear trend among judges to treat possession of child porn as if it's not serious, but these are crime-scene photos," said Ernie Allen, president of the National Center for Missing & Exploited Children.

Mr. Allen says the dissemination of such images encourages behavior that hurts children, not least the production of those images.

Some child-porn viewers still get sentences of 15 or 20 years from judges who follow the guidelines. That's greater than punishments meted out to some child molesters and other violent criminals.

But other judges are openly attacking the practice. "These guidelines are flawed not only because they are duplicative and draconian but most critically because they apply to almost all offenders, allowing no distinction between aggravated and less aggravated behavior," wrote Joan Gottschall, a federal judge in Chicago who recently sentenced a child-porn viewer to six years in prison, rejecting the 20- to 24-year term recommended by the guidelines.

In another example from June 2009, a former schoolteacher in Pennsylvania who downloaded images received a one-day prison sentence, followed by 10 years of probation. The federal judge, Lawrence Stengel, said the guidelines, which recommended four to five years, didn't account for the special circumstances of the case. For example, the judge ruled, there was no evidence that the defendant had attempted to molest any children.

The split among the judiciary means that someone who receives a prison sentence of several years in one court could get a decades-long sentence in a different court.

Last month, J. Randal Hall, a federal judge in Augusta, Ga., sentenced a child-porn viewer to 20 years in prison. There was no evidence that the defendant, Roger Gambrel, who is in his mid-50s, physically abused children, said his lawyer, Jacque Hawk.

"This amounted to a death sentence," Mr. Hawk said.

Write to Amir Efrati at