Two petitions for an Extraordinary Writ of Prohibition are consolidated in this case. The petitioners were initially charged, by *598complaint, with the crime of rape. At their preliminary hearing the petitioners testified as to the consensual nature of their relations with the alleged victim. The committing magistrate dismissed the action on the ground of insufficiency of evidence..
The County Attorney then presented the matter to the Grand Jury, which, after hearing the testimony of the victim and an investigating police officer, indicted petitioners for rape.
Petitioners filed a motion to quash the indictment, which was denied. Thereafter, they separately filed the instant petitions, seeking to prohibit the District Court for Salt Lake County from proceeding further on Grand Jury indictments against them. We issue the writ.
If the Grand Jury violated its express statutory duty as prescribed in Section 77— 19-4, U.C.A.1953, or if it was given no opportunity to exercise that duty, the indictment is void and confers no jurisdiction upon the trial court to try petitioners for the offense charged.
Section 77-19 — 4, U.C.A.1953, provides:
The grand jury shall not be bound to hear evidence for the defendant; but it is their duty to weigh all the evidence submitted to them, and when they have reason to believe that other evidence within their reach will explain away the charge, they should order such evidence to be produced, and for that purpose may require the prosecuting attorney to issue process for the witnesses. [Emphasis added.]
This court has previously stated the aforementioned statute is one of those prescribing the powers and duties of grand juries.1
After the instant petitions were filed, the County Attorney filed an affidavit stating that although the record before the Grand Jury does not reflect the matter, he, in fact, informed the Grand Jury the complaint had been dismissed for insufficient evidence by a committing magistrate.
The evidentiary record of a Grand Jury may not be supplemented by an affidavit of a prosecutor. If it could, the affidavit here does not show the statements of the Deputy County Attorney qualify, under the statutory requirements, to be received as evidence by the Grand Jury.
Section 77-19-3, U.C.A.1953, as amended 1967, provides:
In the investigation of a charge for the purpose of indictment the grand jury must receive no other evidence than such as shall be given by witnesses produced and sworn before them, or furnished by legal documentary evidence, or the deposition of a witness as provided in section 77-1-8. . . . [Emphasis added.]
A question of grave import, implicit in this matter, is whether the Grand Jury may, at its option, determine whether to order the production of evidence which will explain away the charge, after being informed of its availability. Does the Grand Jury have a statutory duty, under Section 77-19-4, to order the production of exculpatory evidence, if it has reason to believe it is within its reach?
The first clause of Section 77-19-4 states the Grand Jury shall not be bound to hear evidence for the defendant; however, the remaining clauses set forth the duties of the jury in regard to evidence. A reasonable interpretation of the first clause is that the Grand Jury need not actively seek evidence exculpatory in character; nor, owing to the secrecy of the proceedings, does one have a right to be informed of the investigation and have an opportunity to present evidence in his behalf. However, the Grand Jury is commanded to weigh all evidence submitted to them. Within the statutory duty clauses, how must the following be interpreted: “When they have reason to believe that other evidence will explain *599away the charge, they should order such evidence to be produced.”
In its historic role, the Grand Jury acts to protect as well as to accuse. Its duty to exonerate, in the face of exculpatory evidence, is not less demanding than its duty to indict, when evidence so requires. The word “should” is defined as being used in an auxiliary function to express duty, obligation, necessity, propriety, or expediency.2 It is clear the term “should order,” read within the historic role of the Grand Jury and the context of the statute, sets forth a statutory duty in mandatory terms.
Both parties cite Johnson v. Superior Court of San Joaquin County3 wherein the court ruled that when a district attorney, seeking an indictment, is aware of evidence reasonably tending to negate guilt, he is obliged to inform the Grand Jury of the nature and existence of such evidence; so the Grand Jury may exercise its power to order the evidence produced. The Johnson case concerned the obligation of the District Attorney to inform the Grand Jury, and the court issued a writ of prohibition on the ground the obligation of the District Attorney had not been fulfilled. The court did not address the issue of whether the Grand Jury was required to order production of the evidence. However, the court observed that Section 939.7, Penal Code of Cal., which is similar to Section 77-19-4, U.C.A. 1953, had a protective role because the proceedings of a Grand Jury are held in secret without notice to the defendant.
The court stated:
. A Grand Jury should never forget that it sits as the great inquest between the state and the citizen, to make accusations only upon sufficient evidence of guilt, and to protect the citizen against unfounded accusation, whether from the government, from partisan passion, or private malice. [Citation]
The protective role traditionally played by the Grand Jury is reinforced in California by statute (Section 939.7) ... 4
In the instant case, there is no evidence in the record of the proceedings before the Grand Jury that it had an opportunity to order exculpatory evidence.
TUCKETT, J., concur.. In re Report of Grand Jury, Shoemaker, et al, v. State, 123 Utah 458, 462, 260 P.2d 521 (1953).
. Webster’s Third New International Dictionary.
. 15 Cal.3d 248, 124 Cal.Rptr. 32, 539 P.2d 792 (1975).
. At p. 254, p. 35 of 124 Cal.Rptr., p. 795 of 539 P.2d.