MORE THAN a decade ago, when Richard Nixon became president, it was widely believed that the Supreme Court's decisions in the Miranda case and its close relatives -- Escobedo, Mallory et al. -- had a short life expectancy. Mr. Nixon made one thing perfectly clear: he anticipated that his appointees to the court would undo the "harm" that these and other civil libertarian decisions were said to have done to law enforcement. Mr. Nixon did appoint four justices, and they and their brethren got a clear shot at Miranda the other day. Miranda survived intact.

The action the Miranda decision required has now become a commonplace scene, not only on the streets but on television's cops-and-robbers programs. "You have the right to remain silent . . . "is the way it usually begins, as an officer explains to those under arrest their legal rights. But there was a second part to the decision. It said that if a suspect wanted to talk with a lawyer, the police had to stop all interrogation until he had had that talk. If they did not, the answers or confessions they obtained could not be used in court.

The horror stories then dreamed up about the impact this straightforward rule would have on law enforcement seem strange now. If suspects were told of their rights, it was said, they wouldn't confess. And if they didn't confess, hundreds of crimes -- mostly the grisly ones -- would go unsolved.

It hasn't worked out that way, of course, because the police responded by doing better investigative work and relying less on confessions, just as the court had suspected they would. Even an old-fashioned law-and-order jurist like Chief Justice Warren E. Burger -- Mr. Nixon's first appointee -- has decided, as he put it earlier this week, neither to "overrule Miranda, disparage it, nor extend it."

What the court had not done until now was to define what constitutes the "interrogation" police are forbidden to conduct after a suspect asks for a lawyer. Does interrogation include only direct questioning? Or does it also include conversations between police officers in the suspect's presence? In the case decided last Monday, the justices had a suspect who was not directly questioned after he asked for a lawyer. But he did lead police to an incriminating shotgun after listening to two officers speculate about the possibility that a child from a nearby school for the handicapped might find the gun first and hurt herself unwittingly.

The definition of interrogation seven of the nine justices agreed upon includes that kind of police conversation only if it is designed to elicit a confession. Five of the seven thought this particular conversation was not so designed. The other two thought it was intended to play on the suspect's emotions and persuade him to point out the gun's location, thus violating the new definition.

That's a close call, either way. While it seems likely to us a majority of the original Miranda court would have sided with the two dissenting justices on the facts of this case, it also seems likely that court would have accepted the same definition of "interrogation." Since, in the long run, definitions and principles are what really matter, it is safe to conclude that Miranda is still -- 10 years after being a prime target for dismemberment -- alive and well.