Recent rulings of child pornography cases in Massachusetts have given offenders a lighter sentence than the U.S. Sentencing Commission has recommended, a pattern that shadows other rulings nationwide.

The median decrease from the commission’s recommended minimum sentencing was 46.7 percent from Oct. 2010 to Sep. 2011 in substantial assistance departure cases, according to U.S. Sentencing Commission data.

Recent child pornography cases in Massachusetts are evidence of such statistics.

In January, Judge Patti B. Saris sentenced a Dedham man to 21 months in prison for possessing child pornography – 42 months less than the punishment issued in the commission guidelines, according to The Boston Globe.

Two years prior, Judge Michael A. Ponsor sentenced a Springfield man to four years of probation and community confinement for possessing child pornography, according to a U.S. Attorney press release. The minimum suggested punishment is six to eight years in prison, according to The Globe.

But a judge in Pennsylvania recently sentenced a tenth-grade teacher who possessed and distributed child pornography to 19 years and seven months in prison, a punishment within the commission’s guidelines and just five months less than the maximum penalty.

The debate arises amidst recent child pornography cases in the Boston area – former elementary teacher David Ettlinger, 34, from Brighton, faces charges of possession of child pornography and now for assault.

Last Thursday, a 54-year-old management company employee was arraigned and charged with possessing child pornography after his employers found material on his work computer.

Although the commission establishes guidelines of punishment for federal crimes, Supreme Court rulings have declared that judges do not have to follow the commission’s suggestions when sentencing offenders.

The commission holds a public hearing on child pornography crimes today in D.C. The hearing will include discussions on technology, sex offender treatment and perspectives from the law, victims and courts.

Jetta Bernier, the executive director of Massachusetts Citizens for Children, said people are trying to research if people who view child pornography go on to molest children, or if pornography deters people from actually going out and risking being caught with a child.

However, she said that just by viewing the material, people are creating a market for that material and kids somewhere are being sexually abused.

One of the fundamental problems of child porn is that children are being sexually exploited in order to produce the material, she said.

“We need to work to prevent child sexual abuse from happening in the first place,” Bernier said.

Some local laws, she said, have expelled offenders from communities, which means such offenders have no place to live.

“We find them clustering in trailer parks, for example, because it’s cheap to live there and because trailer parks tend to be out of the way,” Bernier said. “When you have that happen you have a concentration of those who are sexual offenders and that can be really high risk area for any child to live or visit in.”

Bernier said people need to listen to the judges and understand why they are not following the guidelines.

“I think at this point we have to really listen to what these judges are saying,” Bernier said, “and to allow the legal system essentially to make an informed decision about what the right penalty should be.”