America's Overcrowded Prisons Jammed jails trouble Europe, too.

As crime has soared in France during the past few years, so has prison overcrowding. According to Justice Ministry statistics, some 42,000 Frenchmen are incarcerated - even though the maximum prison capacity is 31,500. Few new prisons are being built.

Compounding the problem is the strictness with which French law treats prisoners. Bail is impossible to obtain in most criminal cases, and judicial powers of ''preventive detention'' are extensive. The result: Some 52 percent of the French prison population has not been convicted of any offense. Moreover, once found guilty, offenders receive no time off for good behavior and no flexible prison terms.

Despite this attitute, the idea that a prison's purpose is to rehabilitate as well as to punish has gained ground. Since the Socialists came to power in 1981 , Justice Minister Robert Badinter has shut down the guillotine, worked to reduce the bench's preventive-detention powers, and started new community-service programs for convicted felons.

Judges now have the option of sentencing convicts to do free municipal work. In the past three years the Justice Ministry has also doubled the number of associations that help convicts avoid prison by finding them temporary housing and work. The convict is then expected to repay his victims.

But these measures have hardly dented the prison problem. A public outcry against rising crime has evoked stiff criticism of Badinter's ''laxism.'' Judges continue wide use of preventive detention, and municipalities have proved unwilling to take on convicts for work programs.

The result: Only about 1 percent of those convicted are taking part of the program.

GlasgowChristopher Andreae

Britain now has a higher number of people in prison per capita than any other country in Western Europe except West Germany.

In England and Wales the average daily prison population stands at 43,029, while ''normal accommodation'' provides for only 39,063.

According to the inspector of prisons, nearly 40 percent of the prison population live two or three to a cell.

The only significant move against overcrowding is a building program. The governement's aim is to complete 14 new institutions in England and Wales by the end of the decade.

In Scotland the overcrowding problem is not quite so extreme. Prisoners awaiting trial are the ones chiefly affected. Scottish judicial procedures deal more quickly than those of England and Wales with prisoners on remand.

In England and Wales the average time people spend awaiting trial is 14.2 weeks. The government, however, is committed to a bill that will introduce statutory trial deadlines and shorten that time. ''At least,'' says Sarah Cawthra of the Prison Reform Trust, ''it means recognition of a problem which before was simply ignored.

A sizable number of noncustodial options are open to British courts in sentencing offenders, but both the Home Office and reform pressure groups agree that they are not much used in England and Wales.

In Scotland, however, a growing number of young offenders have been ordered to perform services to the community over the past five years.

Some critics of the penal system maintain that the root of the overcrowding problem is too-lengthy sentences. A climate that fosters reduced sentences is needed in Britain, they argue. The independence of the judiciary is hotly defended in Britain, however, and the present trend in the courts is toward even longer sentences.