Leroy Hendricks is every parent’s nightmare: a 62-year-old pedophile, convicted five times of molesting at least 10 children over a period of 40 years, who admits that he might well molest more if given the opportunity.

His case, Kansas v. Hendricks, is every civil libertarian’s nightmare.

That’s because, to prevent Hendricks from preying on more children, the Supreme Court may be tempted down the slippery slope of allowing states to lock people up-perhaps for life-based-on inherently Speculative predictions of future dangerousness. Down that slope lie questions like this: If pedophiles can be preventively detained for what Kansas calls a "mental abnormality" predisposing them to molest children- even though the likelihood that they will do so falls well short of certainty-why can’t recidivistic armed robbers, or violent drunks, or others be detained for what might be called a "sociopathic personality disorder," which makes them equally or even more likely to commit other crimes?

At the bottom of the slope lies the specter of totalitarianism, as Justice Antonio Scalia noted during the Dec. 10 oral argument in the case.

Anyone with a grain of concern for civil liberties would hesitate to venture down this slope. But do die justices have a choice, short of telling Kansas that it must free Hendricks until-as Chief Justice William Rehnquist put it-"he goes out and does it again"?

Hendricks is one of thousands of sexual predators who will remain a threat to children as long as they live. Studies indicate that many have had dozens, even hundreds, of victims. Some are in prison, but few are serving life sentences.

Hendricks has served all of his sentences for all of his crimes. Any further criminal punishment at this point is clearly barred by the double jeopardy clause. Nor can he be confined under the usual civil commitment process (which focuses on temporary treatment of patients for their own good as well as for the protection of others): He is neither irrational, nor a danger to himself, nor "mentally ill" (as that phrase is used by the psychiatric establishment). Nor does any known treatment have any real hope of rendering him (or others like him) safe for children.

What to do with an incurable pedophile who has served his time? Just about every Imaginable solution-including "chemical castration," physical castration, and variations on New Jersey’s Megan’s Law, requiring that neighbors be warned about pedophiles recently released from prison-is being tried or considered by various states and Congress. All such measures raise thorny constitutional problems.

The approach adopted in recent years by Kansas and at least five other states is a civil-criminal hybrid providing for continued, indefinite confinement of "sexually violent predators" like Hendricks after completion of their criminal sentences. Other states may adopt similar laws if the Supreme Court gives a green light by upholding the Kansas statute, the Sexually Violent Predator Act of 1994.

The statute describes itself as a new foam of civil commitment for "a small but extremely dangerous group of sexually violent predates" who don’t fit the state’s general civil commitment statute. If, at the end of such a person’s sentence for a crime of sexual predation, a jury finds beyond a reasonable doubt that fee has "a mental abnormality or personality disorder which mates [him] likely to engage in predatory acts treatment and Incapacitation "until such tine as [he] has so changed that- [he] is safe to be at large."

A "predator" like Hendricks is entitled to release whenever he can convince’ the court that these Is "probable cause" to believe that he has changed and can safely be released. But in practice, that may be almost impossible; barring a medical breakthrough, someone like Hendricks seems likely to be locked up until he dies or becomes too feeble to molest anyone.

While the supreme courts of Washington and Wisconsin have upheld similar statutes, the Kansas Supreme Court ruled 4-3 that Hendricks must be freed. The court found that the Kansas law violates substantive due process under U.S. Supreme Court precedents that the majority construed as meaning that if is unconstitutional "to indefinitely confine as dangerous one who has a personality disorder or antisocial personality but is not mentally ill."

The state court found that "the primary objective of the Act is to continue incarceration and not to provide treatment" This finding Is amply supported by the legislative history as well as the preamble, which says that "the prognosis for rehabilitating sexually violent predators in a prison setting is poor," and that "the treatment needs of this population are very long term." It is also supported by the fact that the law provides for no treatment until after completion of the initial criminal sentence, and the tact that Hendricks and others have been confined in a prison-like facility at a state hospital.

Significantly, the state Supreme Court also stressed that (as of 1994) "treatment for sexually violent predators is all but nonexistent” even after they have been moved Into "civil" confinement.

In the fee of this evidence that die Kansas law boils down to long-ten preventive detention, testate and its amici-including 37 ether states, victims groups and some psychiatrists-cite the long tradition of using ‘insane asylums" to Confine incorrigibly violent lunatics even when toe was no red tope off successful treatment They claim that in faet, there now are moderately effective treatment for pedophilia, and that Hendricks is now receiving treatment.

The state and its supporters also stress that the Kansas law Is less restrictive, and more finely tuned, than the clearly constitutional alternative that states might be driven to adopt if this statute is struck down: mandatory life-without-parole sentences for all persons convicted of especially serious acts of child molestation or sexual violence. But it’s too late to give life without parole to many pedophiles, including Hendricks-who, after his latest crimes, plea-bargained his way to a sentence under which he qualified for parole after 10 years, in 1994.

What say the psychiatrists? As usual, it depends on which ones you talk to. The American Psychiatric Association and most other mental health groups are supporting Hendricks, in part on the ground that pedophilia is not a "mental illness" and that mental health professionals don’t have any effective treatment for it.

But other psychiatrists, siding with the state, argue that there’s nothing magic about the words "mental illness," and that requiring a finding of mental illness for civil commitment "would be tantamount to delegating to the psychiatric profession the ultimate determination" of constitutionality-in the words of a brief filed by (among others) the Menninger Foundation, which operates a leading psychiatric hospital In Topeka.

The same brief also claims that there are now "numerous promising treatments" and drugs that may succeed in providing sexual predators with "methods of self-control." But it stops well short of claiming that any treatment now available can be guaranteed to render pedophiles safe.

So the dilemma at the core of this case seems inescapable: The justices must either set Hendricks free-probably to prey on more children-or take a big step down the preventive-detention slope, well past the step it took in United States v. Salerno (1987), which upheld a federal : statute providing for short-term preventive detention of dangerous criminal defendants awaiting trial.

With misgivings, I think the Court should take that step. But it should also carve out a secure stopping point by stressing two crucial limits:

(1) Long-term preventive detention should be imposed only on persons who

(a) have been convicted of crimes that are both driven by some recognized I mental abnormality and cause severe and immediate harm to others-not property crimes, drug crimes, or even armed robberies, for example-and (b) have been proved beyond a reasonable doubt to pose a grave threat of committing more such crimes if released.

(2) Any such detainee must be released if at any time the state cannot prove both that his conditions of confinement are as nonpunitive as possible, and that it is making a serious effort to treat his abnormality with the hope of ultimate release, rather than simply incarcerating him.

As a practical matter, such a rule would apply almost exclusively to sex offenders who are both extremely dangerous and obviously sick (if not "mentally ill"). In theory, psychopathic killers would also qualify, but In practice almost all of them are sentenced to life imprisonment (or death) In any event.

The rule proposed tee would also require Kansas to let Leroy Hendricks go, unless it can mate a stronger showing on remand than it has made to dale that it is providing him with meaningful treatment. For the sake of some child somewhere, let’s hope it can.