"Sometimes, no news is news," says Jim Snyder, news director at WTOP-TV. There was a great deal of no-news during the trial of Maryland Gov. Marvin Mandel, and television brought us all of it. But there will always be a lot of no-news during TV coverage of trials until television cameras are allowed inside courtrooms where they belong.

Television has been around for nearly three decades and portable minicam technology is no longer very new, but only now is Congress seriously toying with the idea of televising deliberations from the House and Senate floors. And there has been very little progress in opening up courtrooms to TV cameras, even during trials of such public figures as Mandel.

After the first trial was declared a mistrial, the second Mandel trial - the one that ended in guilty verdicts yesterday - took 10 weeks. The jury deliberated for 13 days. During all this time, Washington TV stations felt obligated to provide regular reports on the trial even when there was little to report beyond the state of the weather outside the courthouse.

You can't put a camera in a courtroom but you can install an artist and a pad, so that's what everybody does. People who see enough trial coverage on TV and look at enough of those drawings, and then one day actually go to a trial in person, may be surprised to find out that all the people inside the building are not watercolorpastels.

We have to depend on watercolors, chalk sketches and old "Perry Mason" returns for our concepts of what a trial is.

With the present restrictions, trials are not good television - no more than football would be good television if cameras were restricted to stadium parking lots and hot dog stands. Does everything have to be good television in order to justify its existence? No, though there are people in television who think so. But the possibilities in using television to cover trials fully and first-hand are more exciting than the conceivable abuses of access are disquieting.

The whole area of trial coverage, and pretrial coverage, even by prinmedia, is still sensitive and complicated. Lawyers and judges have long warned of "trial by television" just as they warned of trial by newspaper. Even the right to make those courtroom drawings had to be fought for.

But it should be obvious by now that television is not going away; that it is the chief source of news for American households, and that to throw roadblocks between TV news and an event only gives TV newsmen that much better an excuse for superficial coverage.

"The challenge was ours to make it a television story," says Sam Zelman, news director at WMAL-TV. "Since it's a non-television story, we have to use some enterprise in getting pictures. We have an artist in the courtroom, yes. And we catch people coming and going.I though we played it a little heavy while the jury was out - we had to do sidebars and things - but it's suspense story, and people want to know what's happening."

Sometimes this meant, at all the local stations, plopping reporters with nothing to report in front of cameras and letting them report it. Some of the ad-lib advisories got pretty sloopy. What can you - that nobody tried to tamper with the jury while our cameras were trained on the door? That a jet plane did not crash into the courthouse today?

Reporters got trapped on the air attempting innumerable variations on the scoop that there was nothing new to report and that the jury was still deliberating. Of course, this situation wouldn't be much afftected even if cameras had been allowed in the courtroom, because they would never be allowed, one hopes anyway, in the jury room. Yet stations were obliged to keep crews and reporters on hand because you never know when juries will make up their minds.

Zelman thinks situation reports are justified in such a story even when there's no sign of a change in the situation. "You have to report every day while the jury deliberates," he says. "Two or three days ago. The Post had nothing on the trial. That's a mistake. You have to keep people apprised of what's going on."

Synder says he also kept at least one crew at the trial site and had daily reports because "we need to keep people posted. This trial would determine whether a governor of a state would be deposed. We had an obligation to tell people how this came about."

He doesn't think repeated shots of people entering and leaving the courtroom - from the outside of course - were bad television necessarily. "Mandel getting into his car after two days of grilling from the prosecuting attorney was fascinating to watch. There's something about seeing that man and hearing him in that condition that you could only get from television. The newspaper or radio coverage."

We deserve more of television news than the flavor of this one was more fully captured in written accounts anyway. Radio reporters were able to get to the air more quickly with late-breaking poop. For television coverage of a trial like Mandel's to be more truly television, cameras are going to have to invade the courtroom itself.

Except for the few dramatic highlights and, naturally, yesterday's climax, television didn't do much with the Mandel trial other than make it seem considerably less compelling than it could possibly have been.