Can a witness be compelled to testify in accord with their last statement?

As we explained in People v. Fields (1983) 35 Cal.3d 329, 361, 197 Cal.Rptr. 803, 673 P.2d 680: "We recognize that a witness ... is under some compulsion to testify in accord with statements given to the police or the prosecution. The district attorney in the present case obviously believed that [the witness's] last statement was a truthful account, and if she deviated materially from it he might take the position that she had breached the bargain, and could be prosecuted as a principal to murder. But despite this element of compulsion, it is clear, and the cases so hold ... that an agreement which requires only that the witness testify fully and truthfully is valid, and indeed such a requirement would seem necessary to prevent the witness from sabotaging the bargain. We believe the requirements of due process, as explained in Medina, are met if the agreement thus permits the witness to testify freely at trial and to respond to any claim that he breached the agreement by showing that the testimony he gave was a full and truthful account." (Citation omitted.)