When will a witness be compelled to testify on privilege against self-incrimination?

Further, as we have noted, "our Evidence Code provides that when a witness grounds refusal to testify on the privilege against self-incrimination, a trial court may compel the witness to answer only if it 'clearly appears to the court' that the proposed testimony 'cannot possibly have a tendency to incriminate the person claiming the privilege.' (Evid.Code, 404.)" (People v. Cudjo, supra, 6 Cal.4th at p. 617, 25 Cal.Rptr.2d 390, 863 P.2d 635.)