NOT EVERYONE who commits a crime belongs in prison. In many cases it's not necessary; in others, particularly involving juveniles, it's unwise. And to be practical about it, at a cost that often exceeds $25,000 a year per prisoner, society simply cannot afford to incarcerate all offenders. The Attorney General's Task Force on Violent Crime stresses the fact that prisons are overcrowded and points out that between 1978 and 1981 the prison population increased by 60,000. The enactment of a number of mandatory minimum sentence laws and changing public attitudes on sentencing have exacerbated overcrowding. Is the only solution to build more jails?

The American Bar Association, at its recent mid- year meeting, voted to support the development of alternatives to prison sentences for those who do not need to be confined to protect the public. In some jurisdictions these alternatives are already being tested. Using a private foundation grant, the National Legal Aid and Defender Association has projects going in six cities designed to develop sensible sentencing alternatives and to monitor the effectiveness of such penalties. Nonviolent offenders are the best candidates, and most proposals combine two elements: a period of community service with structured hours and strict supervision and a program of restitution to the victim. Some judges also add a short period of confinement or a requirement that the offender spend nights or weekends or both in jail. NLADA is training workers to develop ideas for alternative sentencing and is closely monitoring about 50 cases in each of the project cities. Its final report is due next year.

The Public Defender Service in the District has won praise for its efforts in this area, and an imaginative program in Maryland was making progress until funding ran out. In Anne Arundel County, a project called "This Investment Makes Us Even" (TIME) worked to find jobs for juvenile offenders so that they could make restitution to their victims. After 10 months, the staff of TIME has been reduced to a single person, and she will lose her job in June. This decision is a shortsighted one if it was made on a cost-benefit basis. True, in the first 10 months of the program only $27,000 was returned to victims, while the administrative costs of the project were three times that amount. But surely there are substantial savings that cannot be easily measured. Forty youngsters have been placed in jobs. Many will not commit crimes again. The state is not supporting them in institutions. Their families have had the benefit of some of their earnings, and so have the victims. This program and others like it throughout the nation deserve continued support.