Unlike other crimes, when a sex offender has done his time, he doesn't always regain his liberty. 16 states now have laws that allow civil commitment of sex offenders after their prison sentences are up.

These laws have been upheld in the past--the states argue the men are too dangerous to be released--but new criticism is emerging because the laws often punish mentally ill offenders for their thoughts rather than their actions.

In yearly review hearings, the men are judged by their sexual tastes and fantasies — or what psychiatrists suppose to be their fantasies — as well as their performance on psychological tests, their attitudes toward authority and their willingness to acknowledge their crimes and disorders.

Many are rapists or child molesters — and the fear that they might commit more of the same crimes is grave. In 1998 New Jersey — like other states reacting to murders by sex offenders with previous convictions — authorized the commitment of anyone who has served time for a sex crime and is found to have a "mental abnormality or personality disorder" that makes him likely to commit another crime. These men are to be given treatment — chiefly group therapy — until they are judged no longer dangerous.

Five years later, only a handful have been released, and critics of the commitment process — psychiatrists, civil-liberties advocates and even some early supporters of the law — are concerned that it is merely an exercise rigged to keep sex offenders locked up for a lifetime.

Most of this long article focuses on New Jersey's Violent Sexual Predator Law, since New York Times reporters were granted access hearings there. Yet they report that much of the system is still shrouded in secrecy.

Critics say the hearings deny offenders both the legal protections of a criminal prosecution and the sound medical grounding of a regular civil commitment case. They say the diagnoses — framed by lawmakers rather than doctors — are so vague they could apply to millions of people. By rummaging through a patient's past and psyche, they say, the state can always find a reason to keep him confined.

Several people who have worked in the system told of prosecutors' shopping for psychiatric opinions and of exaggerated, even erroneous testimony and public defenders too overwhelmed to organize a proper defense.

We find the process by which these offenders are kept in indefinite custody very chilling--from the way they are notified they will be transferred to another facility for testing just days before their scheduled release, to the testing procedures and to the small percentage who ultimately gain release.

And in related news, a new Justice Department study shows that sex offenders are less likely to reoffend than other incarcerated offenders: