Fifteen years ago, when I was a federal prosecutor in New York, I led a 13-month investigation of a vast cocaine distribution organization. This organization was based in Manhattan but had spread to four other states and Canada. Ultimately, 18 participants were arrested. All but one either pleaded guilty or were convicted of serious narcotics offenses. The kingpin of the organization was sentenced to 20 years' imprisonment, a substantial sentence by the standards of the time.

The least culpable of the 18 defendants was a 21-year-old woman who played a subordinate and short-term role but technically was guilty of narcotics offenses involving at least 500 grams of powder cocaine. The judge sentenced her to probation.

It was a compassionate sentence and the proper one, given the level of her involvement and the absence of any prior criminal record. After 15 years of additional exposure to -- and involvement in -- the criminal justice system, I am even surer now of the propriety of that sentence.

But if the terms of an amendment passed by the Senate this month had been in effect in 1984, this woman would have received a mandatory minimum sentence of 10 years in prison, even in the face of strong evidence that she was a fringe player and even though there was overwhelming evidence that she was not a drug dealer by trade. Her life would have been ruined, an unnecessary tragedy.

The Senate's action, an amendment to pending bankruptcy legislation, was framed as an effort to shrink the disparity between sentences for crack and powder cocaine. At present, a defendant convicted of dealing at least five grams of crack cocaine in the federal system receives a mandatory minimum sentence of five years. In the case of powder cocaine, the five-year mandatory minimum does not apply unless the defendant has engaged in drug dealing involving amounts of at least 500 grams.

This 100 to 1 disparity has struck many participants in the system as unjust, in part because it has a disproportionate impact on minority defendants -- more than 80 percent of crack defendants are African American. The Senate amendment would lower the weight of powder cocaine that requires imposition of a five-year mandatory minimum sentence to 50 grams and lower the weight that draws a 10-year mandatory minimum to 500 grams.

The appropriate solution, one urged by many participants in the criminal justice system, is to reduce the disparity by raising the weight standard for crack cocaine rather than lowering it for powder cocaine. Unfortunately, this solution runs counter to the iron law of drug politics, which holds that it is politically foolhardy to oppose tougher sentences for defendants involved in drug-related crimes. Indeed, at one level, with an election looming next year, it is surprising that the amendment passed by the narrowest of margins, 50-49.

The combination of mandatory minimum sentences and federal sentencing guidelines has established a schedule of sentences almost unimaginable in its severity to someone involved in the drug wars during the mid-1980s, which predated the era of sentences driven by mandatory minimums and mandatory sentencing guidelines. In general, defendants convicted of narcotics conspiracy or narcotics sales faced penalties ranging anywhere from probation to 15 years in prison. Judges had almost unlimited discretion to sentence narcotics defendants to any period of imprisonment within that range.

There were substantial disparities and inequities in this system: Similarly situated defendants would suffer very different fates depending on the particular judge who sentenced them. These inequities were addressed by the development of the sentencing guidelines. Some say they nearly extinguished judicial sentencing discretion.

Since the late 1980s, sentences available to prosecutors in narcotics cases -- and mandatory within comparatively narrow ranges for sentencing judges -- have become dramatically more severe. Some time ago we reached the point of diminishing returns. Too many lives are unfairly ruined by Draconian sentences that do not achieve the law-enforcement objectives -- primarily deterrence -- supposedly promoted by them.

Although it takes courage for politicians to say in this context that we have gone too far -- or at least that we should go no farther -- we plainly have reached that point. Last month I heard a story that should trouble any advocate of harsher mandatory minimum sentences. A prominent conservative jurist, a Reagan administration appointee, recently presided over a narcotics trial. As in my case, the trial involved a young woman with no prior history of involvement in drug dealing. The evidence showed that she was pressured into participating in the drug transaction by a federal agent but not to the point that the agent's conduct constituted entrapment. The defendant was convicted.

The judge, faced with the legal requirement to impose what he considered a savage sentence, declined to do so. He thought the legally mandated sentence would ruin the defendant's life for no purpose. He refused to apply the law, instead sentencing the defendant to probation. The prosecution waived its right to appeal the judge's improper sentence, implicitly acknowledging the justice of the decision. When prosecutors and pro-law-enforcement judges are so troubled by the mandates of the sentencing guidelines and mandatory minimum sentences that they fail to follow the law, we should not be making sentencing provisions even tougher.

The way to mitigate the unfairness of the crack-sentencing standards is not to toughen the powder-cocaine sentencing rules; it is to take the more courageous step of ameliorating the crack-sentencing scheme. When Congress reconvenes at the beginning of next year, it should reject the powder-cocaine measure that the Senate passed this month.

The writer, a lawyer in private practice, was inspector general of the Justice Department from 1994 until this year.