They determine who to indict, what the charges will be, what witnesses will be called or recalled, and whether to grant leniency to witnesses who might testify against the defendant. A defendant has no right to be present or to have their attorney present at grand jury proceedings. Grand jury secrecy supposedly exists to protect the reputation of the accused, who is not represented there. After the unpunished leaking by the Starr grand juries, this is an attenuated protection. Instead, secrecy works as an effective device to conceal the machinations of the prosecutor.
Federal prosecutors disregard the ethics code that is supposed to bind all attorneys.
The Justice Department does not enforce their regulatory function over prosecutors, and judges have lost the power to oversee prosecutorial abuse due to laws like the federal mandatory sentencing guidelines passed in 1987. Thus the power of the prosecutors grows, and they have become virtually unpunishable. In turn, prosecutors have increasingly adopted an anything goes attitude. In fact, he has all the power. One manifestation of this power is the victimization of defense attorneys who are too energetic or successful.