What is the test for allowing police witnesses to opine that their exculpatory witnesses were lying?

Defendant contends the trial court deprived him of due process by allowing the police witnesses to opine that his exculpatory witnesses were lying. "The general rule is that an expert may not give an opinion whether a witness is telling the truth, for the determination of credibility is not a subject sufficiently beyond common experience that the expert's opinion would assist the trier of fact; in other words, the jury generally is as well equipped as the expert to discern whether a witness is being truthful." (People v. Coffman and Marlow (2004) 34 Cal.4th 1, 82.)