Four years ago, when Congress passed the Brady law, opponents said it was a naive misunderstanding of the criminal mind. Criminals, they said, don't buy guns at the store. They steal them or come about them some other way.

Well, never underestimate the stupidity of the criminal mind.According to the latest estimates from the Justice Department, 69,000 people were denied handguns in 1997 because of the Brady law. Of those, 61.7 percent were turned down because of prior felony convictions or indictments. Another 11.2 percent had a record of domestic violence. In four years, nearly a quarter of a million handgun purchases have been thwarted this way.

Turns out a lot of criminals, at least the ones who have a conviction somewhere in their past, aren't so smart after all. Aren't you glad the Brady law is in place? More to the point, aren't you glad Congress didn't bow to pressure from the gun lobby and reject Brady four years ago?

True, the 69,000 represented only 2.7 percent of the 2.6 million applications for handguns last year. But our guess is 69,000 unstable people could do a lot of damage if they were armed. The small percentage merely proves what researchers, criminologists and, yes, gun lobbyists have said all along - that most gun owners are responsible and law abiding. The trick is to stop the handful most likely to cause mischief.

Brady imposes a five-day waiting period for all handgun purchases to allow for background checks and to keep people from buying guns in a fit of passion. The waiting period is set to expire in November when a nationwide instant background check system is expected to be in place. At that time, the law will be broadened to require background checks for all firearm purchases, not just handguns.

Not surprisingly, the battle lines are being drawn again. President Clinton wants to extend the five-day wait, while gun lobbies, including the National Rifle Association, want it to disappear.

Keeping track of rejected sales is easy. However, keeping track of deaths and injuries avoided through a five-day cooling off period is impossible. The cool down is nevertheless an important argument for making people wait.

Contrary to all the clamoring four years ago, no one has suffered a deprivation of constitutional rights through the Brady law. By some estimates more than 40 percent of American households today contain at least one gun. An extension of the Brady waiting period seems only prudent. It is no doubt a major contributor to the nation's steadily declining crime rate.