1. Who may impeach a Witness
Voucher Rule
The old rule (no longer in existence) was that a party could not impeach its own witness. By calling the witness you vouch for his/her credibility.
Why would one want to impeach his/her own witnesses?
The witness might say something you weren’t expecting that hurts your case.
The witness might have positive and negative testimony and you want to impeach the negative testimony
The witness might have been called as a “hostile” witness in the first place
You might want to bring out fact that will come to light in cross examination in any case, on your own terms.
Evidence Lecture 9

2. Impeachment by Bias
A major way a witness can be attacked is to show that the witness was biased.
Bias includes evidence that the witness is:
Prejudiced against the object of his/her testimony
Has an interest that conflicts with the object
Has any motive to misrepresent the truth or to present it in a manner not favorable to your side.
Bias can be established through:
Showing the bias through questioning the witness
Bringing other witnesses or evidence to the effect that the witness was biased
Evidence Lecture 9

3. Other Impeachment Methods
Impeachment can also be based on any of the following:
Physical defect that affects the ability to have sensed the evidence at issue
Mental defect that impacts the ability to understand and relay the testimony properly
Contradiction with logic or other facts
Prior inconsistent statements
All of these can be done through
Questioning the witness
Bringing other witnesses or evidence to the effect that these conditions exist
Evidence Lecture 9

4. Impeachment by Opinion or Reputation
A witness may be impeached by evidence of character indicating dishonesty. This can be done by extrinsic evidence, as well as by asking the witness.
This can be done through:
Opinion: A third person’s testimony as to his/her opinion that the witness is dishonest or untrustworthy
Obviously, a foundation must be established indicating how the third party formed this opinion…
Reputation: A third person’s testimony that the witness has a reputation for dishonesty in the community
Once a witness’ character has been attacked like this, but not before, the party whom the witness is supporting may “bolster” the witness through similar opinion or reputation witness’ honesty.
Evidence Lecture 9

5. Impeachment Based on Specific Incidents of Conduct
To impeach a witness, one can ask the witness about a prior act on the part of the witness that would serve to impeach credibility. For example:
Did you cheat on your taxes last year?
Did you lie to your boss about being sick last Tuesday?
However:
Only questions about acts that tend to show lack of honesty can be asked.
Unlike most of the other methods of impeachment, external evidence of these acts of conduct (other than criminal convictions discussed on the next slide) is NOT allowed.
Thus, if the witness simply denies the conduct, you’re pretty much stuck with the denial.
Evidence Lecture 9

6. Impeachment By Prior Convictions
A person’s credibility can be attacked by evidence that the witness has been convicted in the past of crime.
Unlike with other specific incidents of conduct, where allowed, evidence of convictions can be proven by extrinsic evidence.
However, for such evidence of prior crime to be allowed, the crime must be either:
A crime involving dishonesty; OR
A crime punishable by more than a year in prison and the judge must determine that the prejudicial effect of the crime being brought up doesn’t substantially outweigh its probative value.
Evidence Lecture 9

7. Impeachment By Prior Convictions - Limitations
In addition to those requirements on the last slide, there are other limitations on the right to bring up past convictions to impeach credibility:
Convictions more than 10 years old are generally not admissible.
Convictions that were later the subject of a pardon are not admissible.
Evidence of a juvenile adjudication is generally not admissible.
Evidence Lecture 9

8. Impeaching the Testimony of a Criminal Defendant
Past convictions are generally not admissible against a criminal defendant unless they fit one of the Article 4 exceptions. However, if a defendant testifies, his or her testimony may be impeached just like any other witness.
Therefore, one has to be very careful about putting a defendant on the witness stand, thus opening the door to past convictions!
If the defendant testifies and the prosecution brings up past convictions, it can only be for the purpose of impeaching credibility.
So, when the prosecutor questions the defendant about the past convictions, the questions must focus on credibility issues - not general character issues.
Evidence Lecture 9