In what circumstances will a district attorney or deputy be permitted to remain in the courtroom during the entire trial?

In the present case, the person permitted to remain in the courtroom was not a stranger to the proceeding but 'the investigating officer,' a person directly concerned therewith. It is, of course, obvious that in a county having a great volume of criminal cases the district attorney or a deputy cannot become fully cognizant, in advance of the preliminary examination, of all of the factual details of each case which he must present before the magistrate. Nor can he personally prepare for every uncertainty or turn of evidence that may occur during the presentation of the case at the preliminary examination. The assistance of the officer who investigated the case is just as essential at that time as it is at the time of the trial in the superior court. With respect to such assistance at the trial, in People v. Boyden, 116 Cal.App.2d 278, at pages 283-284, 253 P.2d at page 777, Mr. Justice White said: 'It has long been the general practice to permit some officer, active in the prosecution of the case, to remain for the purpose of advising the district attorney as to the facts, the interest and character of the witnesses, etc.' Again in People v. Chapman, 93 Cal.App.2d 365, at page 374, 209 P.2d 121, at page 125, it is stated: 'It is the common and usual practice that at least one peace official may remain during the presentation of evidence during the entire case.' See also, People v. Foster, 48 Cal.App. 551, 554, 192 P. 142.