Prosecutors dropped all charges yesterday against three men who had been arrested in the slaying of D.C. housing activist Yulanda Ward, who police said was shot to death during a street robbery last November.

In another development in the case, a fourth man, identified as James Lewis Pannell, 20 of 2832 Hartford St. SE, was charged with murder in the case yesterday. Pannell allegedly shot Ward, 22, when he and other persons held up Ward and three male friends about 3 a.m. Nov. 2 in the 2800 block of Gainesville Street SE, according to police.

D.C. police and prosecutors refused to say yesterday why charges were dropped against the three men originally arrested in the case. But, according to one source familiar with the investigation, people who were with Ward the night she was killed were unable to identify the three original suspects in a police lineup.

Cleared of murder charges yesterday were Sylvester Harrison, 37, of 2315 25th St. SE; William E. Tate, 23, of 1113 Chicago St. SE, and Ernest White, 25, of 9 Hanover Pl. NW.

The new suspect, Pannell, was charged after he was arrested Thursday in an unrelated burglary case.

A police spokesman said investigators had been looking for Pannell in connection with the Ward slaying before he was implicated in Thursday's burglary. Yesterday morning police charged Pannell with the Ward murder after a witness identified Pannell as the person who allegedly shot Ward, according to a police affidavit.

Pannell, through his attorney, pleaded innocent to the murder and burglary charges when he was arraigned late yesterday in D.C. Superior Court. Superior Court Judge Nicholas S. Nunzio set Pannell's bond at $10,000 and ordered him to appear in a police lineup later this month.

Ward was shot in the head at point-blank range after she was separated from her friends and forced to lie spread eagle across the hood of a car, police said.

She was a Howard Univerity student and cochairman of the Citywide Housing Coalition. Ward died shortly after the shooting.