As the great Evidence professor Jerome Prince once instructed: “truth, while never simple, is one of society’s most essential virtues.” For a trial attorney, cross-examination is universally recognized as the preeminent truth-seeking device.
During a cross-examination, witnesses may be impeached by any evidence that tends to discredit their truthfulness or the accuracy of their testimony. Impeachment on cross-examination takes place by many methods – bias, perception, prior inconsistent statements, plausibility, etc.
Police Officers, or law enforcement witnesses, are subject to the same treatment, and held to the same standards as any other witness for purposes of cross-examination. One of the strongest methods for impeaching a law enforcement witness is to confront them with their prior bad acts.
The first foundational element in determining whether one can cross-examine a police officer on a prior bad act is to determine whether the nature of the act “bears logically and reasonably on the issue of credibility.” Each instance is fact specific as this evidence is being introduced to attack the witness’s trustworthiness. It is not character evidence. Character evidence is never permitted to prove that a police officer acted the same way on the particular occasion in question.
The trial judge will then consider whether the probative value of the prior bad act will confuse or mislead the jury or, if it will create a substantial danger of undue prejudice to the officer, essentially performing an FRE 403 analysis, despite the fact that the FRE does not bind the NY State Courts.
The last step in the analysis, but a crucial one, is whether the cross-examiner has a “good faith” basis for the impeachment question. This requires that the cross-examiner have a “reasonable basis” for believing the truth of inquiry.
An illustration of a “good faith” basis to impeach a police officer with a prior bad act may be found in a prior civil suit alleging specific misconduct by the official. Such accusations have been found to constitute a “good faith” basis for questioning the witness about those specific allegations in the complaint. Interestingly, the cross-examiner may not ask the witness if they had been sued or the result of the prior suit. Further, Courts have precluded impeaching with general, non-specific allegations in a lawsuit.
Another instance where Courts have found a “good faith” basis for questioning a police officer about a prior bad act is where a judicial determination has been made that the witness testified falsely in a prior proceeding. So, if a Court has found an Officer’s testimony “incredible” as a matter of law, such a judicial determination satisfies the good faith basis requirement and the attorney may impeach with such information.
With the recent repeal of Civil Rights Law § 50-a, whereby the scope of disclosure of law enforcement witnesses to both criminal defense attorneys and civil plaintiff’s attorneys has changed, the determination on the scope of permissible cross-examination of police officers is in flux and remains uncertain. The best tact is to bring a pre-trial motion requesting permission of the trial judge to cross-examine on this material.
 New York State Guide to NY Evidence 6.11 Impeachment in General (1).
 People v. Smith, 27 N.Y.3d 652 (2016); People v Rouse, 34 NY3d 269 (2019).
 New York State Guide to NY Evidence 6.16 Impeachment of a Law Enforcement Officer.
 New York Stat4e Guide to NY Evidence 4.11. Character Evidence (2)(b).
 New York State Guide to NY Evidence 4.11. Character Evidence (2)(c).
 New York State Guide to NY Evidence 4.11. Character Evidence (2)(a).
 People v. McGhee cited as People v. Smith, 27 N.Y.3d 652 (2016).
 Smith at 661; Rouse at 273.
 New York State Guide to NY Evidence 4.11. Character Evidence Notes.