Impeachment is the process of demonstrating that a witnesses' testimony was inaccurate. You can do this by introducing other evidence that contradicts their testimony. You can also do this by showing that they're a dishonest person in general, but the ways in which you're allowed to do this are VERY limited. You're not allowed, in general, to impeach with "collateral matters" - i.e., proof that they were dishonest in some totally unrelated context. You can introduce evidence that they were convicted of a crime, to impeach them, but only if it was in the past 15 years, and only if it was a felony or a crime of dishonesty such as perjury or forgery.
An impeached witness still gives testimony and the court still considers that evidence; they're just supposed to consider the impeachment as possibly reducing the persuasiveness of that testimony.
Please read the following notice: <br> <br> Jay Bodzin is licensed to practice law in the State of Oregon and the Federal District of Oregon, and cannot give advice about the laws of other jurisdictions. All comments on this site are intended for informational purposes only, and do not constitute legal advice or create an attorney-client relationship. No posts or comments on this site are in any way confidential. Each case is unique. You are advised to have counsel at all stages of any legal proceeding, and to speak with your own lawyer in private to get advice about your specific situation. <br> <br> Jay Bodzin, Northwest Law Office, 2075 SW First Avenue, Suite 2J, Portland, OR 97201 | Telephone: 503-227-0965 | Facsimile: 503-345-0926 | Email: email@example.com | Online: www.northwestlawoffice.com
I agree with Mr. Bodzin's answer. I'd add that you can also impeach a witness by showing that they are biased or have some incentive not to tell the truth. For example, if they have received money or a reduced sentence for their testimony or if they have something to gain from the outcome of the case.
My responses to posts on AVVO are not legal advice, nor do they create an attorney-client relationship. In order to provide true (and reliable) legal advice, an attorney must be able to ask questions of the person seeking legal advice and to thus gather the appropriate information. In order for an attorney-client relationship to exist, you and I both have to agree the the terms of such an agreement.
Even if someone is impeached, they can still be a witness. Impeachment just means showing something about the witness that suggests their testimony is wrong.
You could impeach a witness by showing that they are a dishonest crook, for example.
Or you could impeach a witness by showing that they are somehow biased (for example, if they are the grandmother of one of the parties to the case).
Or you could impeach a witness by showing that they could not have observed what they claim to have observed (for example, if there is a man who claims to have seen the bank robber's face, you could impeach him by showing that they have horrible vision and were not wearing their glasses).
1001 Southwest 5th Avenue
Portland, OR 97204