In an odd coincidence, last Tuesday, Jan. 12, saw both this nation's highest court and our own state Supreme Court grappling with the rights of sex offenders under the law.

In United States v. Comstock, the U.S. Supreme Court heard oral arguments about the federal government's power to indefinitely detain sex offenders. And the Missouri Supreme Court issued an opinion in the consolidated cases of F.R. v. St. Charles County Sheriff's Department and Missouri v. Raynor, in which sex offenders had challenged a residency restriction that prevented sex offenders from living within 1,000 feet of a school or child-care facility and a prohibition on giving out candy on Halloween.

Such cases test the limits of our commitment to fairness, and even the limits of our compassion. What do we owe sex offenders, and how should we treat them? After all, they are guilty of some of the worst crimes imaginable. Does that mean we can simply lock them up and throw away the key?

The U.S. Supreme Court case last week raised a variant of this last question. Congress had passed a law that said if the government determined that sex offenders were still dangerous even after they've finished their federal sentences, it could commit them to custody indefinitely. The oral argument fixed mainly on the powers of the government under the Constitution, but a revealing analogy repeatedly surfaced during the argument. The analogy illustrated very well how unsettled and how driven by metaphors -- and not facts -- our thinking about sex offenders is.

Elena Kagan, arguing for the government, compared the indefinite detention of sex offenders to quarantining those infected with "some very contagious form of drug resistant tuberculosis." In the case of a TB infection, Solicitor General Kagan said, we'd say the government has the power to hold the person for the safety of society. Justice Stevens picked up on the analogy and pressed the attorney on the other side: Doesn't the federal government have the power to quarantine?

The idea that sex offenders are not like ordinary criminals but somehow sick or diseased and have to be segregated from the general population is a powerful one and may operate as a subterranean motivation for much legislation in the area. But the analogy also discloses an ambivalence about how we think about sex offenders. Are they like ordinary criminals (bank robbers, reckless drivers, etc.) who should be punished and then released? Or are sex offenders more like people who are ill, who need treatment and care -- perhaps indefinite treatment and care -- rather than punishment?

Residency restrictions, such as the ones involved in the Missouri cases, are also a form of "quarantine": They keep sex offenders from living in certain areas and keep them from running into (infecting?) the wrong people. At issue before the Missouri Supreme Court last Tuesday was whether such restrictions could apply to sex offenders who had been convicted of their crimes before the laws were passed.

The 4-3 majority, in an opinion written by Judge Michael Wolff (who, like me, teaches at SLU), said that because the restrictions imposed "new obligations" on sex offenders, the law violated the Missouri Constitution's ban on "retroactive lawmaking." Judge Mary Russell wrote the dissent, arguing in part that because the laws didn't affect sex offender's "fundamental rights," the laws were a valid exercise of the state's police power to "protect its youngest, most defenseless citizens."

The majority opinion seems in line with other Missouri Supreme Court opinions in this area. What is unique about this opinion, though, is a lengthy footnote that appears on the second to last page, responding to the dissent's "evident concern" about the recidivism rate of sex offenders.

Citing to the Missouri Sentencing Advisory Commission's 2009 Biennial Report, Judge Wolff noted that "sex offenders have the lowest rate of recidivism" of the five categories of Missouri Felony offenders. That is, sex offenders are less likely to commit any crime two years after their offense than those convicted of drug offenses, violent and nonviolent felonies, or felony driving while intoxicated. (Interestingly, we don't have a registry or residency restrictions for repeat bank robbers.) Facts like these don't fit well with the metaphor of sex offenders as hopelessly and incurably "sick."

The majority's decision didn't rest on this one footnote, and anyway, it's the job of the legislature to make calls about how dangerous certain offenders are and how much they should be punished (within the limits of the law). But statistics such as the ones cited by the majority are sobering. They are a reminder that here, of all places, where we are particularly susceptible to hysteria, we should be sure we are guided by the facts rather than by our fears. As Judge Wolff wrote, "rather than assuming that the rates [of recidivism for sex offenders] are high, one should look at the data."

This is good advice, no matter whether we think sex offenders are sick or merely bad.