REP. CHARLES C. DIGGS JR. (D-Mich.) - one of 13 members and former members of the House who have faced criminal charges or been in prison since the beginning of the 95th Congress - stands guilty on all 29 charges of mail fraud and illegally diverting more than $60,000 of his congressional employees' salaries to pay his personal and congressional bills. These unanimous findings by the 12 jurors do not mean that Mr. Diggs automatically loses his House seat; he said on Saturday that he will stand for reelection next month and, if he wins, will present himself in January for seating, "just as I have" for the past 12 terms. If he does, it would be up to the Democratic caucus to decide whether he should keep his chairmanships.

Mr. Diggs should not retain the chairmanships. When he was indicted, we suggested (just as we had before, when Rep. John Dowdy [D-Tex.], once a member of the District Committee, was indicted on perjury charges and later convicted) that Mr. Diggs might voluntarily relinquish some of his congressional committee responsibilities until the case was concluded - including the chairmanships of the District Committee and the International Relations subcommittee on Africa. The question then was whether he would have sufficient time between the business of defending himself, running for reelection, traveling in Africa and overseeing the various legislative and research efforts that his massive District Committee staff had taken upon itself to handle.

But it is no longer a simple matter of the best use of his time; Mr. Diggs has been convicted of abusing his congressional powers. Having violated that trust for personal benefit, Mr. Diggs should not retain his chairmanships.

In fact, we have long thought the House District Committee should be abolished; any legitimate oversight functions could be handled by a subcommittee, as they are in the Senate. The District deserves the maximum possible freedom from congressional meddling in local affiars. Whatever legislative help the elected local government may need from Congress could be handled easily without the trappings of a full committee. That, after all, is the spirit in which the District's charter was approved by Congress in 1973 - with much help from Chairman Diggs.

To say that Mr. Diggs should step down from his chairmanships is by no means to depreciate his accomplishments in behalf of this city. And it is unfortunate that private problems led him to undermine his political successes. But that is not an excuse for overlooking or belittling his crimes.