Michael McGirt, a 22-year-old unemployed maintenance worker with prior convictions for drug possession, was sentenced to 15 years with a mandatory four-year minimum in prison for selling a $35 packet of heroin to an undercover police officer.

Anurak Kijjadhip, a 36-year-old Thai national, received one to three years -- or about one-fourth as much time as McGirt -- for a $1.4 million heroin sale one assistant U.S. attorney called "the largest prosecuted case ever" by the D.C. police department.

The two sentences illustrate an irony of mandatory sentencing in the District: small-time drug peddlers like McGirt face stiff, predetermined prison terms in D.C. Superior Court, while major drug suppliers, like Kijjadhip, are prosecuted in U.S. District Court, where the sentencing law doesn't apply.

"The people who are selling the drugs on the streets are nickel and dimers," said attorney Daniel Harn. "The people who are really important, they do not use drugs, they do not sell drugs on the street. They have people who are out there selling it . . . . And if they are caught, they get sent to District Court."

U.S. Attorney Joseph E. diGenova, whose office can prosecute cases in either court, said drug conspiracies can be dealt with more effectively in U.S. District Court because of federal racketeering laws and provisions for wiretaps and seizure of assets. Federal agencies, such as the FBI and the Drug Enforcement Administration, are more effective in combatting the conspiracies, he said, and federal grand juries have more time to devote to long-term probes.

Convicted drug distributors, The Post found, are twice as likely to receive a long prison sentence in Superior Court as they are in the federal courthouse. The Post compared the sentences received among 186 felony drug defendants in federal court in 1985 with the punishments received by convicted offenders in the Post's 1983 sample.

Defendants were more likely to be convicted and sentenced to prison in Superior Court in The Post's samples. And, in Superior Court, 56 percent of those convicted of a felony drug charge were sentenced to a year or more in prison, compared with 27 percent in federal court.

As the law's author, D.C. City Council Member John Ray (D-At Large) had argued that mandatory sentencing would guarantee stiff prison terms for important drug traffickers. But he said in a recent interview that he never took into account that the U.S. attorney's office would bring the people he had in mind before federal judges.

DiGenova said he doesn't like every sentence that comes down in District Court, but he described the one given Kijjadhip as "an aberration," pointing to another man who recently received 60 years in prison in connection with large quantities of PCP.

Most defense attorneys, however, said they prefer taking their clients before federal court judges, who they said are more lenient.

"The obvious way to beat the mandatory minimum," said attorney Irvin Foster, "is to go to federal court."