Six elite police drug squad members whose partial acquittals in the slaying of a Miami drug dealer triggered rioting in the city's Puerto Rican community were spared a second trial on unresolved charges. U.S. Atty. Dexter Lehtinen said that after a review his office decided not to seek another trial and filed a motion to drop the case. He provided no explanation. The police officers were acquitted in December on 17 of 24 counts, including conspiracy, but a jury deadlocked on the most serious charge of civil-rights murder. The officers were accused of fatally beating Leonardo Mercado, 35, who was Puerto Rican, and attacking two of his stepsons in 1988.