The leader of a ring that provided LSD to Fairfax County high school students and who tried to elude authorities by faking suicide two years ago was sentenced yesterday to 24 years in prison.

Seth Michael Ferranti, 21, has been in federal custody since his arrest in October in a St. Louis motel. Authorities said they found 18 pounds of marijuana and a dozen different identification cards in his motel room.

Ferranti and five other former county high school students were convicted of conspiring to sell more than 100,000 doses of LSD from 1989 until 1991. Much of it was bought by teenagers in the Burke area who attended Robinson Secondary School, Ferranti's alma mater. He disappeared in November 1991 while awaiting sentencing in U.S. District Court in Alexandria.

The phony suicide was staged on the banks of the Potomac River in Great Falls, where U.S. Park Police found Ferranti's car, clothing, a suicide note and an empty vodka bottle. But police said they never believed he was dead, and the U.S. Marshals Service put him on their list of the 15 most wanted fugitives.

Assistant U.S. Attorney Timothy Shea argued for a strict sentence, saying Ferranti still would be peddling marijuana had he not been caught in October. Judge Claude M. Hilton rejected Ferranti's assertions of remorse.