What is the current state of the law on improper vouching by a prosecutor at trial?

the trial court or the jury, and it is reasonably probable that without such misconduct, an outcome more favorable to the defendant would have resulted. [Citation.] Under the federal Constitution, conduct by a prosecutor that does not result in the denial of the defendant's specific constitutional rightssuch as a comment upon the defendant's invocation of the right to remain silentbut is otherwise worthy of condemnation, is not a constitutional violation unless the challenged action " 'so infected the trial with unfairness as to make the resulting conviction a denial of due process.' " [Citation.]' [Citation.]" (People v. Fuiava (2012) 53 Cal.4th 622, 679.)

" ' "[A] prosecutor is given wide latitude during argument. The argument may be vigorous as long as it amounts to fair comment on the evidence, which can include reasonable inferences, or deductions to be drawn therefrom. [Citations.] It is also clear that counsel during summation may state matters not in evidence, but which are common knowledge or are illustrations drawn from common experience, history or literature." [Citation.] . . .' Nevertheless, '[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. . . . 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," [her] comments cannot be characterized as improper vouching. [Citations.]' [Citation.]" (People v. Ward (2005) 36 Cal.4th 186, 215 (Ward).) "Opposing counsel may not complain on appeal if the reasoning is faulty or the deductions illogical because these are matters for the jury to determine." (People v. Lewis (1990) 50 Cal.3d 262, 283.)