A grand jury is a group of people called together by the prosecutor to gather and review information about suspected criminal activity. After listening to witness testimony and examining evidence, the grand jury decides whether there is enough evidence to issue an indictment charging the defendant with drug crimes. Grand juries are used in the federal system and most states. At the federal level and in some states, grand juries must be used for charging felony drug crimes; in some states, they may be used but do not have to be.