Fairfax County police have seized the tires, front bumper and grill from a Reston woman's Saab 900S, which they believe was involved in a hit-and-run in Herndon last month that killed a man who was sitting under a tree drinking beer.

Efrain Marquez, 35, and two cousins, Clemente Marquez, 33, and Baudilio Marquez, 20, were lounging under a tree in the front yard of 901 Alabama Ave. the night of Aug. 8 when a white car jumped the curb, crossed the lawn and pinned Efrain Marquez against the tree. Police said that the two cousins ran for help but that when they returned, the car was gone and Efrain Marquez was dead.

Efrain Marquez's immediate family--his three children and his longtime girlfriend--lives in San Miguel, El Salvador, but hired the Washington law firm of Chaikin & Sherman two days after the accident to recover damages in the case. The law firm put one of its investigators on the case, lawyer Ira Sherman said yesterday.

According to documents filed with a search warrant in Fairfax County Circuit Court, the investigator called Fairfax police Tuesday to supply the woman's name and address and the fact that she drove a white Saab.

Police went to the woman's home, the search warrant affidavit states, and found the Saab with "numerous splatters of blood" on the front grill, a bumper with a minor indentation, and blue and red material on the front bumper. The investigators then obtained a search warrant and seized not only the car's front bumper and grill but also all four tires and their wheels, to see whether the tire tracks match those left at the scene of Marquez's death.

The Reston woman, identified in the affidavit as Susan A. Plunkett, has not been arrested or charged. Neither Plunkett nor her attorney, Peter D. Greenspun, returned calls yesterday seeking comment.

Sherman said Marquez's family is "quite upset" that authorities have not resolved the case. Fairfax police said their investigation wasn't finished. "We are still in the evidence collection phase of the investigation, which is very active and ongoing at this moment," spokesman Warren Carmichael said.

Efrain Marquez immigrated to Northern Virginia five years ago, seeking to escape the unrest in El Salvador, according to Silverio Coy, another lawyer for the family. "Instead, he ended up being killed on the streets of Herndon," Coy said. He said Marquez had hoped eventually to bring his family to the United States.

Marquez had a son, Ruben, 17, and two daughters, Dinora, 14, and Jackeline, 5, and Sherman said Marquez was sending about $250 a week back to his family from his work as a busboy at a Chinese restaurant in Herndon.