ALBANY — Dangerous sex offenders who a judge and jury decide are likely to continue abusing children after release from prison will be locked up indefinitely in psychiatric centers under a new law announced yesterday.

Before their scheduled release, mental health experts will assess inmates to determine if they pose a risk of committing more sex offenses. A jury will then decide whether a convict is likely to commit future crimes and a judge will rule on confining the offender or putting them under intensive supervision after release, Governor Spitzer and legislative leaders said.

“We in government have a responsibility to do everything we can to protect the public, especially the most vulnerable in society, from clear threats to their safety and well being,” Mr. Spitzer said. “This is especially true when it comes to protecting the public from those individuals whose mental abnormalities cause them to make sexual attacks on others.”

While politically popular, the latest attempt at “civil confinement” of the worst sexual predators faces a likely constitutional challenge.

“A law giving state appointed employees and juries a role in locking someone up indefinitely because he has a mental abnormality and may commit a crime in the future creates a constitutional nightmare,” a spokesman from New York Civil Liberties Union, Bob Perry, said.

JoAnne Page of the Fortune Society, a nonprofit group that helps former inmates, said harsher penalties decrease the reporting of sexual abuse because they make people reluctant to turn in family members, she said, adding that a majority of sex abuse cases involve relatives.

“This is legislation by horror story,” she said. “This is not a law based on evidence and doing what works. It will do precious little to increase community safety.”

The agreement doesn’t sit well where the offenders would be housed, either.

“There are a lot of concerns about it from a community standpoint,” a retired state university administrator and former spokesman for Citizens for a Better Ogdensburg, home to one of the mental health facilities where the sex offenders will be sent, Bryan Felitto, said. Two others will be in New York City and another will be Marcy, near Utica.

“There’s no guarantee these people won’t be released into the community,” Mr. Felitto said. “Who in their right mind would want one of these near them? This is not exactly a magnet for people to move here. It makes zero sense.”

The bill announced yesterday would create an Office of Sex Offender Management to work with corrections and mental health department officials to assess and place the convicted sex criminals.

Mr. Spitzer said about 1,500 inmates in state prison could be subject to civil confinement, but only a few hundred are likely to go through the new process. He estimated the cost at $80 million annually.