GIVEN ITS age and pervasiveness, television can hardly be described as a new or untried technique. But in one respect -- the televising of courtroom proceedings -- it still is both. Whether it will develop beyond this state is now in the hands of the Supreme Court. The justices are deciding whether there is something about television so, well, contaminating that the presence of its cameras in courtrooms fatally infects the purity of legal proceedings.

This question, which has inspired reams of arguments, is ancient. The court came close to eliminating the prospect of courtroom television 15 years ago when four justices were ready to declare that the presence of a camera automatically made a criminal trial less fair than it otherwise would be. Only the fortunate deliberate approach of the late Justice John Marshall Harlan to difficult issues deprived the four of a majority.

Broadcasters have been trying to widen the loophole left by Justice Harlan ever since. Although you would not know it from watching television in this area, criminal trials (or parts of them) are now broadcast all over the country. Maryland became the 27th state to permit at least an occasional television camera in its courts just last month.

There is little evidence that these experiments, or what has gone on in states that have passed the experimental stage, have influenced the outcome of those trials. There is likely to be even less such evidence as time goes on, if the Supreme Court permits the cameras to remain in the courtrooms. The generation of children now in school is beginning to regard cameras, video recorders and their own pictures on the screen as much a part of daily life as bubble gum. It may be that the state court judges, who have permitted all this experimentation with television, are closer to real life than are those members of the federal judiciary who fear the impact a camera will have on a juror's or judge's behavior.

It is possible, of course, that members of the present generation of judges and jurors will act differently if they know they are on camera. But it is not clear such a change would be harmful. We have known some judges who altered their behavior radically, usually for the better, the moment a newspaper reporter entered their courtrooms. The issue, however, is one that can be handled on a case-by-case, state-by-state basis. That is one of the values of a federal system.

In the meantime, if the justices are willing, the general public can begin to get, through television, a better understanding of how the law and the courts actually work. It doesn't take more than one real trial to undermine the myth of Perry Mason. There would be, no doubt, much more interest in and a far greater understanding of the precise issue the justices are now mulling over if they had permitted television to broadcast the arguments they heard in this case. If the justices want to give the influence of television on the quality of justice a real test, they might open their own courtroom to the cameras and tell us later how its presence affected their work.