IT SHOULD BE depressingly clear to anyone who has read even a small part of Post reporter Ed Bruske's detailed four-day series on drugs and legal justice in this city that Washington has an epidemic on its hands that no quick fix of mandatory sentencing can begin to help. On the contrary, the law written by D.C. Council member John Ray and approved at the polls by an overwhelming margin of voters in 1982 has backfired in an explosion of drug-dealing that is defying every legal resource hurled at it.

As Superior Court Judge Steffen W. Graae commented to reporter Bruske, there is no evidence that the mandatory sentencing law has been a deterrent -- but deterrence is almost as difficult to measure as it is to legislate. An obvious conclusion is that mandatory sentencing is a bust and should be repealed; but that alone still would leave the city in the grip of massive drug addiction and trafficking that is preying on the young with frightening allure.

Veteran narcotics detective Steve Finkelberg's assessment is grim: "It's always going to be there, and we're not going to get rid of it." Meanwhile, the peddlers get younger and younger, with the police now arresting kids who are 7 years old for selling cocaine and PCP. When it's the quick route to cash and flash for these kids, what good is some obscure threat of jail -- and an even more likely prospect that the system will work around that mandatory aspect of it anyway? There is the comment from attorney Marian Flynn about her not atypical clients: "A lot of them can't read. . . . They're not ones to get out of Lorton in 20 months and spread the word not to do this. To go to jail is not a really horrible thing. It doesn't frighten them as much as you might think."

And that's if they go at all. The plea bargain, always a tool of the legal system, becomes an even more useful alternative to lengthy trials; and the omission of certain facts about a defendant can lead to his or her exemption from the mandatory sentencing provisions altogether. In fact, only a fraction of those convicted of selling drugs ever receive mandatory minimum terms. The series also points out that those who do wind up in prison are mostly small-time, street-level peddlers rather than the suppliers at whom the law was supposed to be aimed.

If there are any tiny bright spots in this grim picture, they are somewhere in the few drug treatment facilities that are making small headway in returning addicts and addict/dealers to better lives. Yesterday's account of what is being done in Brewster, N.Y., offers hope if not a hard record of successes. Given the proportions of Washington's war against drugs, it is small comfort. But matched against the disaster that is this city's "Legal Overdose" of mandatory sentencing, it is a better way to go.