When, in noisy self-congratulation on cracking a criminal case, the officers of the law prejudice a defendant's right to a fair trial, their chosen response is to excoriate the press. They are usually promptly joined in that exercise, with pious delight, by their legal brethren of bar and bench.

That phenomenon is currently being demonstrated here in Britain, which has successfully conned the world into believing that its trials are sterialized of impurities more punctiliously than a hospital operation room.

The matter has to do with the arrest on the night of Friday, Jan. 2, of a man caught in flagrante with a prostitute in a car patrolling police thought had suspect license plates. By the next day, one of the most high-powered criminal investigation teams ever assembled in England, who had spent five years and some $9 million in the effort, were convinced that they had finally caught "The Ripper." The most deadly killer in the land, he is believed to have murdered and horribly mutilated 13 women, eight of them prostitutes. (Last century's "Jack the Ripper," never caught, killed about half that number, also prostitutes.)

At least the press and public had every reason to believe that the cops entertained that conviction for, on Sunday, amid scenes of enormous jubilation, the combined leaders of the police team held a press conference to announce that the Ripper search was being "scaled right down." The chief constable of West Yorkshire, scene of most of the killings, said, "We are absolutely delighted about the developments at this time." In the most glowing terms he congratulated the arresting officers and extended them "heartfelt thanks." They and their superiors were interviewed and all were photographed with smiles three columns wide for the next day's papers.

Naturally, the episode was the lead story Monday in every British national paper and broadcast. The authorities announced that the suspect, whose name was given as Peter W. Sutcliffe, a truck driver, would be taken to court the next day to face "a serious charge."

If, by the end of the weekend, anyone in Britain was not thoroughly aware that Sutcliffe was suspected beyond doubt of being "The Ripper," it was no fault of the voluble Yorkshire officers of the law, their blue ribbon advisory team and all the joyous cops involved. The press had details of which only they could have been the source.

The popular press in Britain, whose dedication to sex and sex-related violence sometimes makes Hustler magazine look like a hymnal, did their technically superb best -- or worst -- for the Monday and Tuesday papers.Relatives were interviewed and pictured, stories and photographs of the prostitute, happily not yet done in Sutcliffe's auto, and of her professional sisters, were published. Photos were run of all 13 earlier victims. Sensationalism was vitamin-enriched. The Times, Telegraph and Guardian were more restrained, but their lead stories were all on the subject, all carrying the word "Ripper," so that even the sobersides who read only those respectable journals could scarcely have supposed that the hullaballoo was about some routine thug.

Come Tuesday, however, no less an embodiment of the law than Sir Ian Percival, QC, the solicitor general, acting in behalf of his boss, an even loftier embodiment, Sir Michael Havers, QC, the attorney general, sent letters to the nation's newspapers and broadcasters implying that they had been very naughty indeed in prejudicing Sutcliffe's future trial (by this time he had been charged with the murder of the Ripper's most recent presumed victim), that they were violating the principle that a defendant was presumed innocent until proved guilty and, most important, that they were breaching Britain's severe restrictions on pre-trial reporting.

Sir Ian was dead right on all three points. So was a Labor member of Parliament, charging "lynch-mob journalism," and also a certain Lord Rawlinson, QC, saying much the same thing in the lead letter to the editor of The Times of London on Wednesday.

The Times, on the same day, surpassed itself in an editorial so sanctimonious as to deserve being imbedded for perpetuity in a block of congealed treacle. Its burden was that of the eminent MP and QCs: The press has been simply dreadful.

"Rarely in modern times can the media in general have acted with such disregard for the law and the fundamental tenets of British justice," the Thunderer thundered.

Of course, it added, "the police are partly at fault" for having shot off their mouths, which is like saying that Torquemada was somewhat to blame for exacerbating religious persecution.

The press, as The Washington Post's correspondent here, Leonrd Downie Jr., has noted, has now somewhat abated its sensationalism -- less, one suspects, for fear of contempt of court than because it has already reported most of what is worth telling.

But, earlier, what were the media to have done about the weekend press conferences and invitations to the photographers in Yorkshire? Were the reporters supposed to slink back to their homes and only in their boudoirs whispered to their spouses that possibly the police were on to something important? Were the hugely smiling (and in some cases uproariously laughing) photographs of the chief constables to have been put into the top-secret shredders?

If indeed Sutcliffe's future trial will be tainted by prejudicial publicity, it seems clear to at least this onetime student of that problem that the damage done has been only marginally increased by the press's sensationalism and frantic interviewing and by the speculations about the weapons used (that information, too, was supplied by the police) beyond that already done by the mere publication, in that most chaste and righteous journal, of The Times' lead story, two-column headline: "Ripper Suspect Faces Serious Charge."

The question is not merely who is kidding whom. It runs simply to the attempt to abrogate common sense. When a man has been sought for five years, in the most publicized manhunt in the last decade, for committing 13 murders of young women, when a suspect is apprehended, when he is charged with the killing of the 13th victim and when, as was the case, scores of policemen had to hold back huge crowds at the courthouse carrying such signs as "Hang the Ripper," can it be supposed that other human beings can be converted into ostriches?