There are differences between a grand jury and a regular jury. Grand jurors are selected from the same pool of regular jurors, they hear evidence in multiple investigations happening at the same time. They are not impartial bodies. Your attorney will not play any role in the challenging or selection of the grand jurors, as opposed to the regular juror selection process. The grand jury proceedings are secret, and you will not be present when other witnesses testify or evidence is presented to the grand jury.