Can a prosecutor vouch for the credibility of a witness by referring to evidence outside the record?

"A prosecutor is prohibited from vouching for the credibility of witnesses or otherwise bolstering the veracity of their testimony by referring to evidence outside the record. [Citations.] Nor is a prosecutor permitted to place the prestige of [his or] her office behind a witness by offering the impression that [he or] she has taken steps to assure a witness's truthfulness at trial. [Citation.] However, so long as a prosecutor's assurances regarding the apparent honesty or reliability of prosecution witnesses are based on the 'facts of [the] record and the inferences reasonably drawn therefrom, rather than any purported personal knowledge or belief,' [his or] her comments cannot be characterized as improper vouching." (People v. Frye (1998) 18 Cal.4th 894, 971 (Frye), italics added.)

"It is settled that making a record of the terms of a plea agreement requiring a witness to tell the truth does not constitute impermissible vouching." (People v. Williams (2013) 56 Cal.4th 165, 193 (Williams II).) "[T]he existence of a plea agreement is relevant impeachment evidence that must be disclosed to the defense because it bears on

Page 38

the witness's credibility. [Citation.] Indeed, . . . 'when an accomplice testifies for the prosecution, full disclosure of any agreement affecting the witness is required to ensure that the jury has a complete picture of the factors affecting the witness's credibility.' " (People v. Fauber (1992) 2 Cal.4th 792, 821 (Fauber).)