THE MOST SWEEPING change in the proposed federal criminal code concerns what happens after a defendant is convicted.The code, as it passed the Senate, would replace all existing law on sentencing, probation and parole with a system of fixed prison terms, limited parole, and compensation to victims of crime. Vanishing along with the old law would be the premise that criminals are sent to prison for rehabilitation, a premise that was once the cornerstone of federal corrections policy. The proposed code says flatly that judges are to regard prisons as inappropriatte settings for rehabilitation efforts - except in those few situations, such as drug-detoxification programs, where there is no alternative.

This change in policy is not as controversial as you would expect. There seems to be a growing consensus that while some prisoners are reformed behind bars, we do not know enough about how, why or even when such rehabilitation occurs to base policy on the possibility that it will. Prison terms, the prevalent perception holds, are useful only in punishing criminals, deterring them from committing crimes and protecting the public from their deed.

The change in purpose does not mean that federal prisons would have to give up efforts to train or treat inmates. But it does mean the end of indeterminate sentences (e.g., three to 10 years for robbery) and a substantially reduced role for the parole board. A prisoner would know when he entered prison how long he was going to be there, and his release, in most instances, would not depend on his ability to persuade the parole board at some future date that he had been rehabilitated.

Accompanying this basic change is a mechanism designed to smooth out the large differences that exist now in the sentences imposed on similar criminals for similar crimes. A sentencing commission would draw up guidelines for judges to use. These would contain a range of sentences for each kind of crime and each kind of defendant. A judge would not be bound to pick a sentence within that range but would have to explain the reason for any deviation from it. A prisoner whose sentence was longer than the commission had suggested could appeal; so could the government if the sentence were shorter than the recommendation.

That approach to sentencing has received general approval among the experts. But there have been some specific criticisms. One is that it would mean longer terms for most criminals because it would reduce sharply the amount of time off for good behavior a prisoner could earn and because the prisoner would have to serve all of his term unless the judge specified that he could be released early. That criticism seems to us unjustifiable and premature. The code sets shorter maximum sentences than now exist for most crimes and establishes guidelines for the sentencing commission that should produce average sentences much like those now served. Another criticism is that the government should not be able to appeal short sentences. We think that if a defendant can appeal a long sentence, basic fairness requires that the government be able to appeal a short one. That view is reinforced by the recent slap on the wrist given a Houston policeman by a federal judge for the murder of a prisoner.

The proposed code also makes substantial changes in the size of the fines that can be imposed and in what happens to the money the government collects. Maximum fines for almost every offense would go up sharply, reaching $100,000 for an individual and $500,000 for a corporation in felony cases. That increase is coupled with provisions barring fines as alternative sentences (no more 30 dollars or 30 days) and requiring that their size be related to the burden imposed on the individual and his family. All of the money collected in fines would go into a new victim compensation fund. Victims of violent crimes (murder, assault and so on) or their survivors could receive up to $50,000 from the fund to cover medical expenses and loss of earning.

Funds of this type now exist in only a few states. The creation of a federal fund, especially in combination with some other innovations in the proposed code, might provide the spur needed to generate more compassion for victims in the criminal law. One of the other innovations directs judges to consider requiring criminals to make restitution to their victims regardless of what other sentense is imposed. Another gives judges the explicit authority to require individuals or corporations convicted of fraud to notify all those with whom they have had similar financial dealings of the conviction. That would be useful, for example, in large land-fraud cases where many of those who have bought property never realize they have been cheated until it is too late to recover damages.

For many supporters of the proposed code, these proposals for profound changes in the post-trial handling of criminals offset various shortcomings they believe the code suffers from elsewhere. We will discuss some of those shortcomings, especially as they affect civil liberties, in another editorial.