THE STATE of Maryland has been forced to speed the paroles of some 3,000 prisoners as part of a federal court agreement to relieve overcrowding in the Baltimore City Jail. While this may produce some public consternation, judges everywhere are reaching a similar and disturbing conclusion - namely, that overcrowding in jails and prisons must be alleviated even if it requires turning inmates loose.

Recognizing the problem, Maryland officials at various times have tried to make use of a mothballed Navy troop carrier, a broken-down Army stockade government-surplus trailers and, finally, an abandoned East Baltimore factory, which now has been acquired by the government.

Yet nearly half the inmates now in the Baltimore City Jail belong in state prisons. Here, too, inmates have been doubled up in tiny cells; and here, too, a federal judge has forced the state and city to agree to some relief through an accelerated release of certain inmates. Even these measures will offer only temporary relief, though, while the state studies other steps. This point up much of what is wrong with the criminal-justice system nationally. In the first place, jails aren't supposed to be prisons - for prisons are meant to be places where convicted criminals serve their sentences. But in all too many localities today, convicted murderers, armed robbers and others have been winding up in the same ancient warrens alongside people who, say, can't make $100 bail on nonsupport charges or some other lesser offenses of which they are presumed to be innocent until proven guilty . Meanwhile, some violent offenders may have been let free because judges have been reluctant to aggravate conditions of overcrowding.

In any event, the courts are subjecting jails and prisons to greater scrutiny, recognizing that prisoners do not lose all their civil rights when incarcerated. No one yet has established a "model" institution or found the perfect combination of rules for confining people and then returning them to law-abiding roles in society. So the increase in judicial attention to these questions deserves greater public understanding and support - not only for reasons of humanity, but also because so many of those who are crammed into the nation's detention centers will ultimately return to society more embittered than when they left.