Sexual molestation is often a crime of secrecy and deception. Those who commit it tend to be good liars, which is bad for their parole or probation officers.

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Though the recidivism rate for sex offenders is lower than that of the general criminal population, reaction to new crimes committed by those who have been released to the community is much stronger, particularly when the victims are children.

Recent cases in Florida in which sex offenders were accused of new crimes have raised calls for action, and today a Pennsylvania House committee will explore electronically tracking sex offenders.

"It's one thing for a drug addict to slip up and shoot up again. It's another for a sex offender to slip up and offend again. That involves another human being," said Michael Hamel, chief of adult probation for Montgomery County in Eastern Pennsylvania.

But keeping track of a person who has committed a sex crime isn't easy.

"A lot of them have been fooling people for years, doing the same behaviors for nearly their whole life, hiding it from everybody," said Chris Murphy, deputy chief under Hamel. "We get fooled."

Montgomery County is one several jurisdictions more aggressively supervising those released to the community after being charged with or convicted of sex offenses.

Parole officers go frequently to the home and workplace of the offender. They hook him up regularly to a polygraph and work closely with his therapists and local victim advocates to keep track of him.

It's one response to the frustration and outrage that erupt when convicted molesters are charged with new crimes after their release.

In Florida last week, the House passed a bill named after Jessica Lunsford, a 9-year-old girl who was abducted and killed last month, that would make a global positioning system device mandatory for offenders convicted of molesting children younger than 12.

A convicted sex offender, John Evander Couey, 46, is charged with sexually assaulting and murdering Jessica. David Onstott, accused in the slaying of 13-year-old Sarah Lunde near Tampa this month, was convicted of a sex crime in 1995.

In Harrisburg, the House Republican Policy Committee is scheduled to meet today to explore the possibility of tracking convicted sex offenders via satellite, using global positioning systems to keep tabs on the offenders' exact whereabouts. Representatives will meet with law enforcement agents and officials from VeriTracks, a Virginia company that supplies tracking devices.

Those who have been involved in efforts to prevent such horrific cases say a comprehensive approach is needed.

There are approximately 265,000 sex offenders under supervision or control of the government in the United States, and about 60 percent of them are free -- on probation, on parole or awaiting trial.

Laws requiring sex offenders to register with law enforcement have been passed by all 50 states since 1996 when Congress enacted Megan's Law, which calls for warning communities of sex offenders in their midst. Many states use electronic monitoring to keep track of people.

At the federal level, the 2003 Protect Act shifted the burden in federal detention hearings to the defendant, who has to show that he's not a danger, instead of making the government show that he is.

The law also toughened sentencing for child sex crimes and gave judges the option of imposing probation for life on sex offenders after they get out of jail. So far in Pittsburgh, the only judge who has used that option is Senior U.S. District Judge Alan Bloch.

No law makes it possible to constantly peer over an offender's shoulder, much less into his brain. The best anyone can do is watch him, talk to him, check up on him, and try to figure out what he's thinking.

"The big goal is to prevent re-offense," said Scott Matson, research associate at the Center for Sex Offender Management, a nonprofit group based in Silver Spring, Md., that receives funding from the U.S. Justice Department and advocates a victim-centered or "containment" approach.

Pennsylvania doesn't have a statewide system for supervising sex offenders, but currently is reviewing practices statewide, said Diane Dombach, executive director of the state's Sexual Offender Assessment Board, which is responsible for deciding whether sexual offenders should be subject to Megan's Law requirements.

Dombach said practices advocated by the Center for Sex Offender Management are widely accepted, and that many of them are in place in the state. A two-year study will help determine whether the state will move toward a statewide system like that in Colorado. Creating a program that works means understanding the way a sex offender thinks. The Center for Sex Offender Management in its materials points out that there is no one typology of a sex offender, but it makes some broad characterizations.

"The vast majority of sex offenders are not mentally ill and do not commit their sex crimes because of such an affliction," according to the center. "Sex offenders engage in their abusive and criminal behavior for diverse and complex reasons, and they often create complex facades to conceal their crimes."

Most plan their crimes for hours, days or weeks ahead of time. Except for those with serious mental illness, they know that their abusive behavior is wrong and illegal. Nevertheless, they often rationalize their behavior, convincing themselves that they are not really committing a sex offense. And when they are accused of such crimes, they try to convince others of the same thing.

Hamel said his team consists of regular parole officers, but a grant from the Pennsylvania Commission on Crime and Delinquency allows them to work overtime to handle their sex offender case loads.

"They see them on an intensive basis, at least twice a week," said Hamel. "They are seeing them in the community, in their home. They have contact with the treatment provider."

He also has a "computer cop" program to see if the offenders are going online to look at porn, and a polygraph examiner on the team for what he calls "reality testing."

"Whether sex offenders are having fantasies or having improper contact with others, we don't know until we sit them down with the polygraph," Hamel said.

Though polygraph exams are not admissible in court and have been criticized as unreliable, their use with sex offenders is standard practice, said Dombach. Those who use them say they serve a purpose.

"We had an offender in here," Murphy said. "He said the victim was crazy, she had made up the whole story.

"Our polygraph office is right across the street. I said, 'OK, you're telling me this, let's go.' I walked this guy across the street, and by time I got back to my office the phone was ringing and [the polygraph operator] was saying 'He's admitting everything.' "

The inclusion of victim advocate groups as members of the team is another prong of the model.

"The victim advocate approach has typically been removed from a lot of work people do with sex offenders," said Matson. "It's been thought of as offenders' rights vs. victims' rights. We realized that there's a tremendous amount of overlap -- why not work together on this?"

Victim advocates "might get them to ask, 'Are our notification policies harming victims?' 'Should we be out leafletting the community of an offender if the victim lives there -- are you outing the victim's father?'"

Larry Likar, an FBI agent for 23 years who specialized in investigating crimes against children and is now assistant professor and chair of the Criminal Justice Department at La Roche College, said the approach advocated by the Center for Sex Offender Management is solid, but that paying for it is always an issue.

"These things sound great until the grant money runs out. When you hear 'grants' or 'special program' it's a problem."

Ironically, the intense supervision being advocated is directed at a population with a relatively low recidivism rate. Though rates vary with the type of sex offense, for all sex offenders they are lower than for the general criminal population.

However, some data suggest that child molesters re-offend at much higher rates than other offenders -- as much as four times higher. Furthermore, many sex crimes are not reported or do not result in an arrest.

"The problem is they can be offending and we're not going to know about it," said Likar. He said the low rates of recidivism found in studies is a "specious" statistic "because we know their whole method is to get away with this crime. They're not stupid -- the ones that are out there. Obviously the ones that are stupid you catch relatively rapidly."

"The recidivism rates are relatively low for those who are in treatment and being supervised," said Murphy of Montgomery County. "They will act out when they are comfortable. If you're seeing them a minimum of once a week and in treatment, it's not comfortable."