The U.S. Department of Justice has encountered considerable difficulties in obtaining an indictment against Sidney Lori Reid, a woman accused of assaulting an F.B.I. agent in Washington, D.C. Prosecutors have attempted to secure a grand jury indictment three times without success, marking an unprecedented situation in the legal system. Legal experts note that the process of obtaining an indictment usually favors the government, making these repeated failures particularly noteworthy. The case has raised questions about the standards and procedures in federal prosecution.