Is a plea agreement that grants immunity to a witness in a sexual assault case valid?

Moreover, plea bargaining is not inconsistent with Penal Code section 132.5. Plea bargaining has a long history in the criminal justice system. Plea bargaining is a practice that is well circumscribed by safeguards to assure that testimony does not violate an accused's right to a fair trial. " ' "[A] defendant is denied a fair trial if the prosecution's case depends substantially on accomplice testimony and the accomplice witness is placed, either by the prosecution or by the court, under a strong compulsion to testify in a particular fashion." ... Thus, when the accomplice is granted immunity subject to the condition that his testimony substantially conform to an earlier statement given to police ... or that his testimony result in defendant's conviction ... the accomplice's testimony is "tainted beyond redemption" and its admission denies defendant a fair trial. On the other hand, although there is a certain degree of compulsion inherent in any plea agreement or grant of immunity, it is clear that an agreement requiring only that the witness testify fully and truthfully is valid.' " (Italics omitted.) (People v. Sully (1991) 53 Cal.3d 1195, 1216-1217, 283 Cal.Rptr. 144, 812 P.2d 163.)