You could say it started with three small-town Minnesota boys riding their bikes to a convenience store on an October night in 1989. As they were returning home on a dark stretch of road, a man stepped out of the darkness holding a gun. He told them to lie face down on the ground and then directed two of them -- Trevor Wetterling, age 10, and Aaron Larson, 11, to run into the woods and not look back or he'd shoot them. That was the last that they, or anyone, would see of 11-year-old Jacob Wetterling.

The subsequent fruitless search led President Bill Clinton to sign a law in September 1994 designed to help police quickly locate potential perpetrators of sex offenses. The Jacob Wetterling Act required states to create sex-offender registries accessible to police, though not to the public. But that same year, 7-year-old Megan Kanka of Hamilton Township, New Jersey, was lured across the street, then raped and murdered by a neighbor who -- unbeknownst to her parents -- had served six years in prison for aggravated assault and attempted sexual assault on another child. The Kankas maintained that, had they known a convicted sex offender lived nearby, they could have protected their daughter. So in 1996, Clinton signed Megan's Law, which required states to open up their sex-offender registries to the public.

Megan's Law launched America's practice of notifying neighborhoods of where sex offenders live. Though the law is well intentioned, it's not clear whether it has reduced the number of sex offenses; rather, public notification appears to destabilize offenders' lives, increasing the risk they'll commit another crime. There is also ample evidence that since the law passed, vigilantes have used sex-offender registries to threaten, harass, and inflict violence on hundreds of offenders and their families.

In the decade and a half since Megan's Law was passed, public-policy researchers, corrections officials, and treatment professionals have begun to recognize the faulty premises and poor outcomes the law has created. A few states, recognizing the problems with public registries, have tried to develop legal solutions that both protect offenders from abuse and reduce sexual violence. But a new federal law -- the Adam Walsh Act, signed by President George W. Bush in 2006 and set to take effect this summer -- threatens to shut down those innovations; states not found in compliance by July 26 will lose critical federal crime-fighting funds. At a time when criminal-justice policies are increasingly adopting a "smart on crime" approach grounded in research on what works, the legal treatment of sexual offenders is moving in the opposite direction.

"Jeff" isn't his real name. When he talks about the June day in 2005 that the beer bottle shattered his front window, his voice quavers. "I'm sorry -- all of this just makes me so angry," he says. He was convicted in 1995, as a 23-year-old, for having what he says was consensual sex with a 15-year-old girl he met in a bar. That onetime liaison came to light, Jeff says, when the girl became pregnant (he says DNA later showed he wasn't the father) and her parents reported the episode to the police, with the girl as a cooperating witness. He spent five years in prison, but even after his 2000 release, state law required that he be placed -- for life -- on the state registry, which shows his photo, address, and the details of his conviction.

Jeff says the bottle thrower on that June day was a neighbor -- someone with whom he'd been friendly -- who had found Jeff on the registry and appeared on his lawn with two biker buddies, shouting threats. When Jeff went out to talk to the group, the men formed a semicircle, pushing and spitting on him. He retaliated with punches, and the resulting fight ended with both sides bloodied and a hole in a wall when they pursued him as he retreated into the house.

A month later, Jeff recalls, his tool shed was broken into and the equipment for his logging business stolen. Not long after, a second neighbor plugged a culvert they shared so that Jeff's basement flooded in the next storm; Jeff says the man told him he'd done it "to get the sex offender out of my neighborhood." Jeff has changed his phone number a dozen times after repeated threatening calls.

In 2003, Jeff married a lifelong acquaintance who knew his history. She worked as a nurse at a hospital, and shortly after their marriage, a manager told her that she had to choose between her job and her husband. Jeff attributes their 2005 divorce to his status on the sex-offender registry: "We were looking at each other, and it was like, 'I'm destroying your life.'" Even the two girls he parents, ages 13 and 14 (one from a previous partner and the other for whom he serves as guardian), started being teased in school and were excluded from social, school, and church events. "What have my kids ever done to anybody?" Jeff says. "In reality, sometimes I wonder if maybe killing myself may not be the best thing I can do for them."

About 700,000 sex offenders appear on registries in the 50 states and other U.S. jurisdictions. But their crimes vary widely, from chronic violent sexual predation down to voyeurism and even public urination. Researchers estimate that the vast majority of these offenders are at low-risk for repeating their crimes. Nonetheless, the public is overwhelmingly concerned: In a 2005 Gallup poll, 66 percent of respondents said they were "very concerned" about sex offenders, while 36 percent said the same about terrorism.

Giving a nervous public instant access to the addresses and photos of sex offenders produces none-too-surprising results. Though no reliable national statistics exist on vigilante violence against sex offenders, a few studies indicate widespread abuses. In a 2005 study by University of Louisville criminologist Richard Tewksbury in the Journal of Contemporary Criminal Justice, 47 percent of 121 sex offenders reported they'd been harassed as a result of being on a state registry, and 16 percent said that they'd been assaulted; among nearly 600 immediate family members of offenders that Tewksbury and Lynn University researcher Jill Levenson surveyed, 44 percent said they'd been threatened or harassed by neighbors as a result of their relative's sex-offender status, 27 percent that their property had been damaged, and 7 percent that they'd been physically assaulted or injured. A 2005 study in the same journal by Levenson and Leo Cotter, who directs a Florida sex-offender outpatient program, reported that 21 percent of 183 offenders had their property damaged by a person who found out about their status.

Recent incidents illustrate those findings. In April 2010, a man used a printout from California's sex-offender registry to try to rob the homes of two registered sex offenders in Grover Beach. In November, a registered sex offender from Orlando was assaulted in front of his home by three teens who told him they knew he was a sex offender; they punched and kicked him repeatedly and stomped his dog to death before running off. That same month in the Virginia town of Hopewell, police charged 19-year-old Daniel Narron with attempted murder for using his SUV to try to run down 52-year-old Rudolph Ellis, who is on Virginia's sex-offender list. Since 2005, at least six sex offenders nationwide have been murdered by people who used a state registry to track their victims.

The problems with the sex-registry laws are myriad, starting from their very premises. One of the basic assumptions behind Megan's Law is that parents who know that a sex offender lives nearby will take precautions; after a decade and a half, however, there's little research to show that's happened. A second premise is that sex offenders are somehow different from other criminals and can't change, but a 2003 study found that sex offenders had a three-year recidivism rate of 5 percent for another sex crime; that compares with a 47 percent rate for other criminals committing another crime. Finally, the law assumes sex offenders will be less likely to commit another crime if they know they're being watched. Again, the research is weak: In 2009, analysts at the Washington State Institute for Public Policy looked at seven studies on recidivism by registered sex offenders that had been conducted since the first registry law was passed. Two showed that being on a registry decreased recidivism, one showed an increase, three indicated no effect, and one didn't measure the effect. "Though the research differs somewhat from state to state and study to study, overall it does not appear that registries have resulted in a significant decline in sex crimes in general or in recidivistic sex crimes more specifically," says Levenson, perhaps the leading researcher on the effects of sex-offender registries.

Still, probably the biggest issue with registries is who gets on them and what happens to those who do. As originally conceived in the Wetterling Act, registries were to be accessible only to law enforcement. It was raw public pressure, rather than criminological research results, that turned those lists over to the public. And, like many policies driven by public furor, the enabling laws overreached. Today, most registries include offenders busted for a range of acts, from offensive or vulgar behavior to heinous crimes. A 2007 Human Rights Watch study reported that at least five states required those convicted of offenses related to adult prostitution to be registered, 11 states did the same for those guilty of public urination, and 25 did so for public exhibitionism. "Most people assume that a registered sex offender is someone who has sexually abused a child or engaged in a violent sexual assault of an adult," noted the study's authors. Registries, that is, create the impression that neighborhoods are thick with recidivist sexual predators, making it impossible for parents to discern who actually is dangerous.

Sex-offender registries also now include people who have committed no sexual crime: Forty-one states put those convicted of falsely imprisoning or kidnapping a minor on their sex-offender registries -- whether or not the crime was related to sex. Last March, for example, the Wisconsin Supreme Court upheld a ruling that a 17-year-old boy who forced another 17-year-old to go with him to collect a drug debt could be made to register as a sex offender, though the crime involved nothing sexual. The court majority argued for the wider net because "Wisconsin's sex offender registration statute 'reflect[s] an intent to protect the public and assist law enforcement.'" As the dissenting justices noted, under that reasoning, convictions for violating most provisions of Wisconsin law could trigger mandatory sex-offender registration.

Sweeping everyone onto a single list produces some absurd outcomes. Fred Berlin, who founded the Sexual Behaviors Consultation Unit at Baltimore's Johns Hopkins Hospital, worked with a patient in his 80s who had Alzheimer's and was living in a nursing home. The man also was on the sex-offender registry for fondling a child in his family. Berlin says the man's offense probably was related to the onset of his dementia. But that didn't stop the nursing home's neighbors, who found his name on the registry, from successfully demanding he be moved to another facility.