Voir Dire in Cases Involving Police Credibility

If police credibility is a critical issue at trial, the defense needs jurors to believe one of two possibilities – the police officers are not credible either because they are mistaken or because they are dishonest. Are the prospective jurors open to the idea that police officers will lie under oath? What hypotheticals can defense counsel use to educate the members of the venire while simultaneously searching for cause challenges?