EAGER TO BE seen as tough on crime, Maryland Gov. Robert L. Ehrlich Jr. (R) and one of his leading Democratic rivals, Baltimore Mayor Martin O'Malley, are outdoing each other to slam sex offenders, with each man proposing to stiffen the penalties imposed on the convicted. First, Mr. O'Malley urged a six-point plan, whose headline-grabbing centerpiece was a draconian requirement that sexual predators and child molesters who have already served their sentences be subject to electronic monitoring for life, possibly by use of satellite-tracking ankle bracelets equipped with Global Positioning System technology. Then, Mr. Ehrlich urged tougher penalties for sexually violent criminals, whom he called "the worst of the worst." Not to be outdone, a Democratic state senator, Ed DeGrange, is crafting legislation that would enable Maryland to lock up certain categories of sex offenders in mental institutions after their release from prison, a sanction in use by 17 other states.

Public revulsion at sex offenders is powerful; their crimes, particularly when children are the victims, can inflict lasting damage and ruin lives. Hence the requirement that sex offenders be listed on post-incarceration public registries -- a method of tracking and monitoring ex-convicts that does not apply generally even to murderers and drug dealers. But the understandable zeal to protect prospective victims goes too far when applied to entire categories of ex-convicts -- individuals who have already paid their debt to society. Even if it makes for campaign trail bravado, clamping ankle bracelets on offenders for life is over the top, and it is unlikely to prevent attacks or help victims. And while it is commonly presumed that recidivism rates for sex offenders are drastically higher than for other categories of criminals, a growing body of research has cast doubt on that presumption.

Maryland prosecutors say they know of no particular surge in the incidence of sex crimes. Rather, the current focus on the problem seems animated by news reports of registered sex offenders in Maryland, Idaho and Florida who assaulted or murdered children after having been released from prison, either while on bail or parole. When emotion, fear and hyperbole drive the public policy debate involving sex offenders, the likelihood of tough legislation by stampede is increased.

Society has a legitimate interest in protecting children and others from sexual abuse. Civil liberties cannot take a back seat. There is a need for sound legislation that distinguishes between offenders who can be rehabilitated or who can be treated psychiatrically with a high probability of success and those who cannot. It makes sense to maintain an up-to-date and accurate registry of sex offenders; and in some cases additional monitoring, including by electronic means, may also be warranted. But election-year calls for harsher punishment across the board, including lifelong GPS surveillance for whole classes of offenders who have already served their time should be mitigated by more rigorously analyzed and tailored proposals.