In a grand jury investigation, Penal Code section 939.71 requires the prosecution to present exculpatory evidence if it is aware of it. If the prosecution fails to comply with its disclosure duty and the failure results in substantial prejudice, the indictment is to be dismissed. Substantial prejudice in the context of a grand jury proceeding is “the reasonably probable test” i.e., after evaluating the entire record, is there a probability that a properly informed grand jury would not have indicted. In this murder investigation, the prosecution misstated information in a manner that strengthened its case and omitted evidence that directly contradicted its key witness. As a consequence, there was a serious doubt as to whether the grand jury would have found a strong suspicion of guilt. Accordingly, the appellate court granted the writ of mandate ordering the indictment vacated.