ALBANY- New York will now keep the most dangerous sex offenders locked up after they complete their sentences.

“Throw away the key,” said 84-year-old Ted Granata Sr., the father of a woman killed by a convicted sex offender, as Gov. Eliot Spitzer signed the bill into law Wednesday. Granata's daughter, Concetta Russo-Carriero, a 56-year-old legal secretary, was stabbed twice in the heart in 2005 by a convicted sex offender after his release from prison.

At Wednesday's signing of the civil confinement law, the woman's son, Jonathan Russo, said the measure will stop “another deranged animal hellbent on violence or sexual assault.”

Under the law, before a sex offender is released from prison, mental health experts will assess inmates to determine if they pose a risk of committing more sex offenses. A jury will then decide whether the convict is likely to commit future crimes and a judge will rule on confinement or intensive supervision after release.

While politically popular despite its high cost - $80 million a year to confine an estimated 100 or so offenders - the law faces a likely constitutional challenge.

“Think of the cost to those innocents who are out there,” countered Senate Majority Leader Joseph Bruno.

About 1,500 prisoners could be subject to civil confinement, but Spitzer, a former prosecutor, said a rough estimate is that the system would yield about 100 offenders who would be confined in secure mental health facilities and another 250 would be closely monitored.

New York is the 19th state to enact a civil confinement law.

“There is a lot more to be done ... when it comes to protecting people from sex crimes,” said Assembly Speaker Sheldon Silver.

“It's a tough bill, it's a smart bill and it's going to do what it's supposed to do - protect our children,” said Senate Minority Leader Malcolm Smith.

The homeless man convicted of stabbing Russo-Carriero was sentenced in September to 25 years to life by a judge who called him “the face of evil.”

“She's missed terribly every day,” her son said.