Santa Clara, Calif., is home to more than 3,000 convicted sex offenders.
But they are not just blending into the community. One law enforcement task force is on a mission to conduct random, unannounced checks on a few of them.
"These are people who have just gotten out of prison or jail, who are likely to re-offend," says Sherriff Lori Smith.
Santa Clara County's aggressive approach to monitoring rapists and child molesters is rare.
In Cleveland, ABC affiliate WEWS-TV found sex offenders living within a few hundred feet of a school. That makes them in violation of state law, and no one is doing anything about it.
The problem of what to do with sex criminals after they are released from prison is a national challenge.
There are more than 700,000 sex offenders in America -- a nation within a nation -- and the recidivism rate among them is 24 percent. That's below the average for all criminals, including drug addicts, but still frightening to law enforcement.
"I don't want them offending again," says Smith. "And if there are steps we can do in law enforcement to keep them from offending, especially sex crimes, I think that's what we need to do."
Back in the 1950s, that was the hope. And in a great social experiment, sentences for sex crimes were reduced.
But by the 1970s and '80s, Americans were demanding harsher sentences.
"There are studies that show that sex offenders on average serve about three years for offenses committed against children," says Rachel Barkow of New York University.
Today, researchers say treatment can help, to a point.
"We can never say that they will never do it again or that somebody is definitively cured or not cured," says Prof. Cynthia Calkins Mercado of John Jay College of Criminal Justice in New York. "But we do know looking across large groups of studies that generally speaking that treatment helps to reduce the number of new sexual crimes."
In Santa Clara, the sherriff's task force found a convicted child molester with toys and other materials sometimes used to "groom" young potential victims.
There's a popular belief that sexual predators of children cannot be cured and should be locked up for good. Americans tried that once, then tried leniency, and now, it seems, are clamoring for a return to the older, harsher approach.
Information about the sex offender registry in your state can be obtained by calling the Parents for Megan's Law hotline at 888-ASK-PSML (888-275-7365).
There is also a national list, the National Sex Offenders Registry, coordinated and maintained by the FBI's Crimes Against Children Unit, which is based on information supplied by states.