Recent focus on the state budget has brought to light efforts to keep some underused prisons open, despite low crime rates and sharp decreases in inmates making them unnecessary. This year New York State will pay $33.5 million to operate four prisons that had been eyed for closure, and another $30 million to renovate them.

Upstate politicians defend the expense by saying that the low New York City crime rate, which now makes the prisons unnecessary, will begin to reverse, when the “next crack epidemic” hits. They also say the investment is needed to keep corrections officers and prison support staff working in towns with no other economic engines. Both positions are out of date and misguided.

The courts and prosecutors have learned many lessons from the crack epidemic and one of these is that you cannot prison-build your way to public safety. In Brooklyn, our approach to drug-related crime is our Drug Treatment Alternative to Prison program, or DTAP, developed in 1990. DTAP combines residential drug treatment with job training, to get addicts off drugs and into legitimate, tax-paying careers. Only nonviolent felony offenders are offered DTAP.

In a 2003 report, Columbia University’s Center for Alcohol and Substance Abuse wrote that DTAP graduates were 87% less likely to return to prison than addicts who had gone to prison instead of the treatment program. Additionally, drug courts throughout New York State, established in 1995 by Chief Judge Judith Kaye, have realized similar recidivism reductions.

The next crack epidemic, already seriously affecting other parts of the country, seems be from the use of methamphetamine, or “meth.” Meth originated in Hawaii and soon spread to the mainland. In Brooklyn we have had a few of these cases and expect more. We have sent meth addicts to DTAP, employing the same techniques we have used on crack addicts for years, and we have had the same success.

Programs like these will insure that crime levels will not significantly rise if drug use increases again, as we saw in the 1980s.

Our ability to divert these new offenders into treatment and return them to society as job-ready taxpayers will reduce recidivism and increase public safety, eliminating the need to waste more than $63 million maintaining and operating empty jails. After two years of counseling and training, when people arrested at the same time are just starting to serve lengthy prison terms — at great cost to the state — DTAP graduates are working at legitimate jobs and paying taxes.

DTAP is used only by one-third of New York State prosecutors, but not because they are unwilling. The state has yet to fund DTAP to the level where it can be employed by every district attorney’s office in New York. It requires at least one assistant district attorney to coordinate the program. But many small, upstate district attorney offices operating with only a dozen or so prosecutors lack the staff to operate a program like DTAP. Public defenders offices also may require additional staff to represent defendants as they work through the program. Finally, residential drug treatment centers also need more funding.

Closing down those four prisons would free up far more funding than DTAP would need to spread across the whole state.

And the real concerns of displaced corrections officers could be addressed as well by retraining them for new professions, possibly in support roles at drug treatment centers. If we can train drug-addicted career felons and help them get jobs, we could certainly find work for hard-working former corrections officers, possibly as drug counselors.

Mr. Hynes is the district attorney of Kings County.