With prison populations that have swelled by factors of six or eight over the last 25 years, many states, including California, are facing real problems regarding overcrowding and the tremendous expense of incarceration. The problems are likely only to get worse; a recent Pew study warns that prison populations will grow by another 13 percent over the next five years.

For these reasons, many states are rethinking their sentencing and rehabilitation policies. For their model, they are looking to New York. Running counter to the nationwide trend, the prison population there has dropped by 8,000, from a high of 71,000 in 1999. (The total number of inmates rose again last year by about 500.)

Most of the decline can be attributed to a drop in crime. Crime in New York -- including in New York City -- has gone down even as the prison population has gone down. Those who have argued for incarcerating more criminals contend that putting bad guys away has helped bring crime rates down. Criminologists believe that is partially true, but they argue that at a certain point you are incarcerating nonviolent offenders, rather than any more of those who are truly dangerous.

New York State is also running several programs to help those whose crimes were not violent to shape up their act. A series of legislative efforts dating back about a dozen years have resulted in prisoners earning time off their sentences for good behavior or success in academic, vocational and drug treatment programs.

The state, meanwhile, has been presenting violent offenders with longer sentences. "The length of stay for inmates serving violent crimes has increased," says a spokesman for the state corrections department. "Our programs should not be confused with a pass card for getting out of jail free."

The reduction in the number of inmates has meant that vacated parts of Rikers Island, the main prison in New York City, are now mainly used by TV and film crews. Governor Eliot Spitzer has proposed creating a commission that would look at closing some of the state's unused prison space.

It's a controversial proposal, opposed by the prison guards union and by upstate legislators from districts where prisons are major sources of jobs. But having an argument about what to do with surplus capacity is much better than the position of many states, which are having to release inmates early or consider doing so because they can't afford to house them.

"No matter how many prisons you build, you're going to fill them up. That's one lesson people have learned over the last 25 years," says Michael Lawlor, chairman of the Connecticut House Judiciary Committee. "New York got the crime rate down and incarceration down at same time. It's the only state that cut prison population."