Can a prosecutor personally vouch for a defendant's guilt?

One form of prosecutorial misconduct is personally vouching for a defendant's guilt. "When arguing to the jury, it is misconduct for a prosecutor to express a personal belief in the defendant's guilt if there is a substantial danger that the jurors will construe the statement as meaning that the belief is based on information or evidence outside the trial record [citation], but expressions of belief in the defendant's guilt are not improper if the prosecutor makes clear that the belief is based on the evidence before the jury [citation]." (People v. Mayfield (1997) 14 Cal.4th 668, 781-782, disapproved on other grounds in People v. Scott (2015) 61 Cal.4th 363, 390, fn. 2.) " 'It is always improper for a prosecutor to suggest that a defendant is guilty merely because he is being prosecuted or has been indicted.' [Citation.] It is equally improper to imply to a jury that an underlying factual predicate of a crime must be true due to the fact of indictment or prosecution." (Washington v. Hofbauer (6th Cir. 2000) 228 F.3d 689, 701-702.)