THE GRAND JURY IS FREQUENTLY THE ONLY MEANS WHEREBY THE COOPERATION OF WITNESSES AND/OR BASIC SOURCES OF EVIDENCE CAN BE OBTAINED. IMMUNITY LAWS HAVE EXPANDED IN SCOPE AND NUMBER AS THEIR EFFECTIVENESS HAS BEEN RECOGNIZED. CONSTITUTIONALITY HAS BEEN DETERMINED WITH RELATIVE FINALITY. PROSECUTORS USUALLY DETERMINE WHETHER IMMUNITY SHOULD BE GRANTED, AND FREQUENTLY SUCH DETERMINATIONS ARE MADE WITHOUT REGARD TO WHETHER A WITNESS WANTS IMMUNITY. GRAND JURY INVESTIGATIONS RARELY PROCEED WITHOUT PRODUCING SOME PERJURIOUS TESTIMONY THAT IS OFTEN PROSECUTABLE. IN MOST JURISDICTIONS, NEITHER THE PROSECUTOR NOR INVESTIGATIVE PERSONNEL ARE ABLE TO COMPEL POTENTIAL WITNESSES TO SUBMIT TO INTERVIEW OR TO PRODUCE PROPERTY AND DOCUMENTS. A GRAND JURY SUBPOENA, HOWEVER, IS A COMMAND BY THE COURT TO APPEAR AND/OR BRING CERTAIN PROPERTY. SUBPOENAS, IN THE HANDS OF EXPERIENCED INVESTIGATORS, CAN BE A VALUABLE TOOL TO AID THE INVESTIGATIVE PROCESS. BECAUSE OF THE DANGER ASSOCIATED WITH PREMATURE GRAND JURY INTERROGATION, PERSONS SHOULD NOT BE BROUGHT IN FOR INTERROGATION UNTIL CAREFUL PREPARATION THAT MUST PRECEDE THE INTERROGATION SHOWS THAT QUESTIONING WILL BE PRODUCTIVE AND NOT DESTRUCTIVE IN TERMS OF SUBSTANCE AND STRATEGY. SIGNIFICANT PREPARATION IS NECESSARY EVEN FOR COOPERATIVE WITNESSES. PREPARATION FOR HOSTILE WITNESSES EXTENDS INTO STRATEGIC AREAS. FOR THESE WITNESSES, IT IS ESSENTIAL THAT INTERROGATION BE DEFINITIVE, INFORMED, AND WITH SUBSTANCE. FINANCIAL RECORDS CONSTITUTE AN IMPORTANT SOURCE OF EVIDENCE. TIMING IN INVESTIGATIONS IS CRITICAL, AND PLANS SHOULD BE MADE FOR CONTINGENCIES AND FOLLOWUP AND FOR PROCEEDINGS IN AS MANY INVESTIGATIVE DIRECTIONS AS POSSIBLE SIMULTANEOUSLY. MOST GRAND JURY INVESTIGATIONS EVENTUALLY REACH THE POINT WHERE THE PROSECUTOR MUST DECIDE WHETHER TO CALL PUTATIVE DEFENDANTS, AS WELL AS POTENTIAL DEFENSE WITNESSES, BEFORE THE GRAND JURY. AS THE USE OF THE GRAND JURY AS AN INVESTIGATIVE TOOL HAS INCREASED, LITIGATION CONCERNING ALMOST EVERY ASPECT OF GRAND JURY OPERATION HAS ALSO RISEN. THE COURT MUST DECIDE ALL CONTESTED ISSUES OF PRIVILEGE, AND THE MOST COMMON ASSERTION OF PRIVILEGE OTHER THAN SELF-INCRIMINATION IS THE ATTORNEY-CLIENT PRIVILEGE. THE UTILIZATION OF IMMUNITY LAWS AND PERJURY LAWS AS INVESTIGATIVE TECHNIQUES IS REVIEWED. (DEP)