Is it proper for a witness to change their testimony from the previous testimony?

the witness to not materially or substantially change his or her testimony from the statements previously given to law enforcement. On the other hand, such testimony is proper when the testimonial agreement suggests the prosecution believed the prior statements were the truth, and the witness understood that his or her sole obligation was to testify fully and fairly. (Id. at p. 455.) This is so even when the witness is legally deemed an accomplice. (People v. Avila (2006) 38 Cal.4th 491, 594; see 1111.)