In what circumstances must a jury reject counsel's argument that the witness was not credible?

they were not credible based on their gang membership or affiliation, their prior crimes, and their motive to lie, jurors must have rejected counsel's argument. We may not reconsider the jurors' credibility determinations. " '[C]onflicts and even testimony which is subject to justifiable suspicion do not justify the reversal of a judgment, for it is the exclusive province of the trial judge or jury to determine the credibility of a witness and the truth or falsity of the facts upon which a determination depends. [Citation.] We resolve neither credibility issues nor evidentiary conflicts; we look for substantial evidence.' " (People v. Letner and Tobin (2010) 50 Cal.4th 99, 161-162.)