On cross-examination, the attorney may want to show the court that the witness should not be believed. A witness' credibility may be impeached by showing evidence of the witness' character and conduct, prior convictions, and prior inconsistent statements. If the witness testifies differently from the information in their sworn affidavit, it may then be necessary to "impeach" the witness. That is, the attorney will want to show that the witness previously said something that contradicts the testimony on the stand.
Impeachment may be done by comparing what a witness says on the witness stand at trial to what is contained in the witness' affidavit. By pointing out the differences between what a witness now says and what the witness' affidavit says, the attorney shows that the witness has contradicted himself or herself.
Who May Impeach?
Any party, including the party calling the witness, may attack the credibility of a witness by:
1. Introducing statements of the witness which are inconsistent with his/her present testimony;
2. Showing that the witness is biased;
3. Attaching the character of the witness in accordance with the state mock trial competition rules of evidence and procedure;
4. Showing a defect of capacity, ability, or opportunity in the witness to observe, remember, or recount the matters about which he/she testified; and
5. Proof by other witnesses that material facts are not as testified to by the witness being impeached.
Conviction of Certain Crimes as Impeachment
A party may attack the credibility of any witness, including an accused, by evidence that the witness has been convicted of a crime if the crime was punishable by death or imprisonment in excess of 1 year under the law under which he was convicted, or if the crime involved dishonesty or a false statement regardless of the punishment, with the following exceptions:
1. Evidence of any such conviction is inadmissible in a civil trial if it is so remote in time as to have no bearing on the present character of the witness.
2. Evidence of juvenile adjudications is inadmissible under this subsection.
Prior Statements of Witness
1. When witness is examined concerning his prior written statement or concerning an oral statement that has been reduced to writing, the court, on motion of the adverse party, shall order the statement to be shown to the witness or its contents disclosed to him.
2. Extrinsic evidence of a prior inconsistent statement by a witness is inadmissible unless the witness is first afforded an opportunity to explain or deny the prior statement and the opposing party is afforded an opportunity to interrogate him on it, or the interests of justice otherwise require. If a witness denies making or does not distinctly admit that he has made the prior inconsistent statement, extrinsic evidence of such statement is admissible. This subsection is not applicable to admissions of a party-opponent.
3. Re-direct and re-cross examination/questioning. If the credibility or reputation for truthfulness of the witness has been attacked on cross-examination, the attorney whose witness has been damaged may wish to ask several more questions. These questions should be limited to the damage the attorney thinks has been done and should be phrased so as to try to "save" the witness' truth-telling image in the eyes of the court. Re-direct examination is limited to issues raised by the attorney on cross-examination. Re-cross examinations follows re-direct examination but is limited to the issues raised on re-direct only and should avoid repetition. The presiding judge may exercise reasonable control over questioning so as to make questioning effective to ascertain truth, avoid needless waste of time, and protect witnesses from harassment.