Does the Attorney General have any authority or authority to compel a district attorney to produce evidence of a 'deal'?

The Attorney General suggests that the district attorney disbelieved petitioner's testimonial description of a 'deal.' A prosecutor may doubtless make preliminary estimates of credibility for his own guidance, but here he forestalled a judicial body's independent judgment of the credibility of existing, sworn testimony. The grand jury, not the district attorney, was the arbiter of probable cause. (Pen.Code, 939.8, fn. 2, supra; Lorenson v. Superior Court, 35 Cal.2d 49, 55, 216 P.2d 859.)