A critical aspect of a criminal defense is the credibility of prosecution witnesses. Our State Constitution through Article 1, Section 9 as well as the 6th Amendment to the United States Constitution permits a defendant to confront the witnesses against him/her. This confrontation is often times done through the defense attorney’s cross examination and an attempt to impeach the witness’s credibility by demonstrating bias, self-interest, motivation to testify favorably and even lie.
In many cases, prosecution witnesses are former co-defendants of the accused or are charged with some other criminal offense themselves. It is important to understand that whenever a prosecution witness may be possibly biased in favor of the prosecution because of outstanding criminal charges or because of some non-final criminal disposition; that possible bias must be made known to the jury. In Pennsylvania, prior to our States Supreme Court’s decision in Commonwealth v. Evans, 511 Pa.214(1986) the general rule permitted the admission of a witness’s unconvicted bad acts only where the defense could demonstrate the witness’s interest in the immediate matter. Prior to Evans, Pennsylvania permitted the defense to introduce evidence of unconvicted bad acts if the criteria was satisfied or if the defense could demonstrate that the prosecutor promised leniency in another case. Following the Evans decision, however, Pennsylvania now allows the introduction of a witness’s unconvicted bad acts or non-final criminal disposition if the defense can establish that the witness is being prosecuted by the same prosecutorial authority. In Evans, the Court reasoned that such evidence is relevant to a witness’s credibility. Even if the prosecutor has made no promises, on the present case or another case, the witness may hope for some favorable treatment if he/she testifies in a way helpful to the prosecution. If the defense is able to establish this possibility, the Court should allow the introduction of this evidence.
In addition to evidence of bias because of unconvicted bad acts prosecuted by the same authority, the defense may always introduce a witness’s prior convictions for those crimes involving elements of fraud, deception, or some other dishonesty. In addition, Pennsylvania allows the admission of evidence of a witness’s character by way of his/her reputation in community for truthfulness or untruthfulness. While the defense may not attack a witness’s character through specific instances of conduct, it may use these specific instances during a cross examination in certain situations.
It is important to always keep in mind that a prosecutor represents society. His obligation is not to seek a conviction, despite what people may think, but to seek justice. This obligation requires him/her to reveal any favorable evidence which would be material to the accused’s case. If the prosecution fails to reveal this evidence it could result in a reversal on appeal and/or a new trial. The right of an accused to favorable evidence is protected by the 14th Amendment to the United States Constitution under the due process clause. In 1963, the Unites States Supreme Court in Brady v. Maryland affirmed this Constitutional right.
It is important that your attorney explore the possibility of favorable evidence and witness bias. Your defense is often based on a witness’s incredibility and the failure to explore this area could result in severe consequences.