How have the courts dealt with the issue of due diligence to secure the presence of a witness at a preliminary hearing?

In People v. McDaniel, 157 Cal.App.2d 492, 499, 321 P.2d 497, two investigators for the district attorney's office testified that they made inquiries as to the whereabouts of the witness and ascertained that he was in Dallas, Texas; that they sent a telegram to an address in Dallas furnished by his family and read a telegram in reply from the witness stating he would be unable to appear at the trial. Photostatic copies of the telegrams were received in evidence and the court held that the testimony of the witness given at the preliminary hearing was properly read in evidence at the trial. It was further held that if, in the exercise of a reasonable discretion, the court determines that a witness is outside the state, its order allowing the testimony taken at the preliminary hearing to be read will not be disturbed on appeal.

As is said in People v. Horace, 127 Cal.App.2d 366, 369, 273 P.2d 923, 925:

'The question as to what will constitute due diligence to secure the presence of a witness which will authorize the reading of such witness' testimony taken at the preliminary hearing when such witness is shown to be unavailable, is largely within the discretion of the trial court and depends on the facts of each particular case.' See also People v. Robinson, 149 Cal.App.2d 342, 345, 308 P.2d 442.