Is it improper for a police officer to render an opinion about whether a child is telling the truth?

(1995) 33 Cal.App.4th 37, 44 [officer improperly testified that "a robbery 'is what happened in this particular case'"]; People v. Sergill (1982) 138 Cal.App.3d 34, 39 [improper for officers to render an opinion about whether child was telling the truth].) Nonetheless, defendant did not provide the trial court with an opportunity to either rule on the admissibility of the detective's testimony or instruct the jury on the appropriate consideration of it because he did not, at any time, voice a concern that the detective's testimony was infringing on the jury's province to determine credibility. Defendant's failure to object to the testimony forfeited the appellate claim.