What is the test for inadmissibility of a voluntary confession in a criminal case?

3 It would be immaterial whether the inadmissibility rests on constitutional grounds. Counsel can be ineffective in more prosaic ways, such as by failing to block oral testimony of the contents of a writing. (Evid.Code 1500). Unless the trial court explores the reasons for such a failure, it would not know whether what is taking place is a deprivation of the right to effective representation, a right which, presumably, the client cannot waive intelligently unless someone explains the best evidence rule to him. Of course, at such a hearing it may appear that counsel's inaction was a tactical decision within his professional province. (Henry v. Mississippi, 379 U.S. 443, 451, 85 S.Ct. 564, 13 L.Ed.2d 408.) The point is, that without an exploratory inquiry by the court, we would not know what it was.

4 For example in People v. Cheatham, 263 Cal.App.2d 458, 463, 69 Cal.Rptr. 679, it was argued that a voluntary confession made to an ordinary witness might have been illegally obtained because the record did not affirmatively show that the person to whom it was made, and who had not advised the defendant of his constitutional rights, was Not a policeman. The logical extension of defendant's point would require the trial court to determine the status of the person to whom the confession is made so that, if it was a policeman, it could then explain to the accused that his attorney can object to the admissibility of the confession. Only then can the accused intelligently waive his right to keep the confession out.

5 We stress again that the chemical nature of the powdery substance is not what the trial was about.