A. If a witness is granted immunity in return for evidence, none of his testimony or any evidence obtained as a fruit of his testimony shall be used against him in any criminal prosecution except that such person may be prosecuted for any perjury committed in such testimony or in producing such evidence, or for contempt for failing to give an answer or produce evidence.
B. Witnesses shall not be harrassed [harassed] nor subjected to unreasonable repeated appearances by the grand jury or the prosecuting attorney assisting the grand jury.