The chilling abduction this weekend of a 5-year-old Fairfax County girl has stunned every parent who has heard about it. The girl was apparently kidnapped from her home and assaulted while her parents slept. Police said this weekend it remained unclear whether the little girl was sexually assaulted. Her parents realized she had been taken only after their daughter made her way back home and told them she’d been hurt, according to The Post story.

Cases like this are the reason we’ve created a system to not only punish but also track child predators. You’d better believe any sentient parent would want to know if a lunatic like this one is lurking nearby.

That reaction, George Mason University cultural studies professor Roger N. Lancaster says in a new book, has led us down a dangerous legal path.

Lancaster’s “Sex Panic and the Punitive State,” (University of California Press, 2011) argues that our reaction to rare child abductions and stranger abuse has created a system that is grossly unjust.

He and I had an e-mail exchange on the subject last week, before the Fairfax abduction. Given the news, it’s an especially raw, but also relevant, time for Lancaster to explain why he thinks we need to reconsider our child predator laws. Here’s our back-and forth:

Q: In “Sex Panic,” you make the case that our sex offender registries are neither fair nor effective. Many parents appreciate these lists both for a sense of security that a sex offender will not be living nearby and that they can determine where “predators” are. What’s wrong with keeping registries? Do these lists give parents a false sense of security?

Lancaster: The unknown person living somewhere in the neighborhood isn’t the main risk to children’s safety and well-being. Most perpetrators of child sexual abuse are family members, close relatives or someone known to the family. Stories of abduction, rape, and murder by strangers excite the worst fears. But these are exceedingly rare events — comparable to the chances of being struck by lightning. And only a very small percentage of sex crimes are committed by repeat offenders, which does suggest that the registries mislead parents.

But I’d suggest that instead of giving a sense of security, false or otherwise, what the registries actually do is to stoke unnecessary parental anxieties. They foster perpetual dread: It becomes everyone’s duty to be constantly alert to remote dangers. Sociologists who’ve studied these practices talk about how they undermine trust, create a culture of fear and fuel a rage to punish. This is bad for adults. And many who have studied the subject think that this is bad for children as well. . . . A study in the U.K. found that excessive fear of predators has contributed to keeping kids indoors, producing a sedentary lifestyle, obesity and other health risks.

Q. You compare the recidivism rate of sex offenders to perpetrators of property crimes. As a society, isn’t it of a higher concern to try to prevent the recidivism of sex offenders (and murderers?)

Lancaster: The goal of preventing recidivism for brutal, violent crimes, including the abuse of children, is obviously a higher priority than, say, preventing recidivism by shoplifters. But recent studies have found no evidence that current sex offender laws and procedures reduce recidivism or that they reduce the number of victims.

The point is that we have an ever-expanding, ever more expensive apparatus — which has never shown to be effective — for managing a problem (sex offense recidivism) that is small in numbers and has declined since the 1980s.

Q. In terms of fairness, why should we be concerned that punishments for child sex offenders are harsh? Aren’t these criminals the worst of the worst?

Lancaster: I’d make two arguments here, one based on principle, the other based on practice.

On principle, the legitimacy of law rests on the premise that punishments are proportionate, that judgments are dispassionate and that laws and penalties are announced prior to events, not tacked on afterwards. These are not liberal or modern ideas; they go back to the founding of rational law, to the ancient Greeks. Reasonable people might disagree over what might count as harsh or excessive, but they shouldn’t disagree over the idea that law should not punish more than is necessary.

In practice, it is not only the “worst of the worst” who’ve been swept up and entangled in sex offender laws. Some of the registrants had consensual relations with near-adults. Others appear to have been falsely accused and accepted a plea bargain. Some were themselves minors who had consensual sex with their girlfriends or boyfriends. A random sample of one state’s listings shows that two-thirds of the registrants were convicted of non-violent first offenses — and their crimes may have involved no physical contact.

The idea that violent repeat offenders ought to be “incapacitated,” as they say when speaking of long prison terms, is one thing. But what we have in practice is a system of perpetual punishment for a growing host of lesser offenses. . . . So I have argued that it’s time to revisit our laws, which are founded on unreasonable fears and a boundless rage to punish.

Q. Strictly speaking in terms of child sex offenders, what might be a better approach?

Lancaster: You could start by comparing U.S. practices with British practices. The British have sex offender registries, too — but a far smaller portion of the population is listed, and yet a smaller portion of registrants are deemed high risk. In England and Wales the ratio of registered sex offenders to the general population is 46 per 100,000; in the United States the ratio is more than 4.5 times greater: 228 per 100,000. The overwhelming majority of British registrants are classified as “Level 1” (on a three-level scale); they are said to pose minimal public risk and are subject to minimal supervision. And the registries are a closely guarded secret, available only to police, parole officers and authorities who might be involved in supervising an ex-convict’s doings. So we could start by scaling back the lists, taking them out of the public domain and professionalizing the supervision process. There’s no evidence whatsoever that this would compromise public safety.

Where a person previously convicted of a sex offense lives or works has no bearing on whether he commits more crimes. But variants of “Jessica’s Law” evict sex offenders from living, working or sometimes even walking within 1,500, 2,000 or 2,500 feet of a school, park, bus stop or place where children might gather. Such laws uproot sex offenders and their families; they scatter them to remote or rural locations. We should rethink this approach, which resembles techniques of governance in authoritarian or even totalitarian states.

While pruning back punitive or excessive measures, I’d also take some positive steps. I’d start with better counseling services for the victims of abuse. But part of what has happened in the last 30 to 40 years is that children have been viewed in terms of threats to safety but not in terms of their overall well-being. Obviously, there’s a lot of work to be done to improve education, nutrition and exercise.

Q. What else might parents want to consider about sex offender registries and child sex offenders?

Lancaster: Parents might be concerned that in a culture ruled by fear, their children could get caught up in sex offender laws. Young children have found themselves on sex offender registries and not invariably for brutal acts. Minors who had sex with their boyfriends or girlfriends have been labeled sex offenders. Teens have been prosecuted for “sexting.” When thinking about crime and punishment, it’s a good idea not only to think of the stranger somewhere in the neighborhood but of the son or daughter in the house.

What do you think? Does Lancaster have a point?