Written by attorneys · grounded in primary & secondary sources — see below
Evidence offered to demonstrate that a witness has a relationship, interest, or allegiance creating a motive to slant testimony for or against a party. Such evidence is always relevant because it assists the jury in assessing the accuracy and truth of the witness's statements. It may be shown through cross-examination or extrinsic proof, including membership in an organization whose tenets require members to lie or give favorable accounts on behalf of fellow members.
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Cases
Study Supplements
How it applies
Common Examples
3
Hacker Collective Membership Questioned
Inventor Maya Ortiz sued CipherCore for misappropriating her encryption algorithm. CipherCore engineer Elena testified that the firm developed the code independently. On cross-examination, the prosecutor asked Elena about her membership in an underground hacker collective whose code requires members to lie to outsiders to protect one another regarding data breaches. The court permitted the questions because the evidence tended to show Elena had an incentive to favor CipherCore's account.
Fraternity Pledge Explored on Cross
Maria Lopez sued Dr. Daniel Chen for malpractice after a misread MRI. Chen's colleague Dr. Evan Ross testified that Chen met professional standards. On cross-examination Lopez asked Ross about his membership in a professional fraternity whose written pledge requires members to give misleading testimony to protect one another from legal trouble. The court allowed the inquiry to let the jury evaluate whether Ross had a motive to favor Chen.
Pena-Rodriguez v. Colorado137 S. Ct. 855, 861 (2017)
Longshoreman Fellowship Inquiry Allowed
Dawn Vessel sued Summit Ocean for cargo damage. Longshoreman Terry testified that the containers were properly sealed. On cross-examination Dawn Vessel asked Terry about his membership in the Seafarers' Divine Fellowship, whose practices encourage members to give favorable accounts shielding the shipping line from liability claims. The court permitted limited questions so the jury could assess whether Terry had an organizational motive to slant his testimony.
Warger v. Shauers135 S. Ct. 521 (2014)
Common questions
Frequently Asked
5
How is bias shown when a witness belongs to an organization?+
A cross-examiner may ask about membership in a group whose tenets require members to lie, cheat, or give favorable accounts on behalf of fellow members. This evidence directly supports an inference that the witness has a motive to shade testimony. The trial court has broad discretion over the scope of such cross-examination.
Supporting sources
Does bias evidence require proof that the witness actually lied in the present case?+
No. Bias impeachment focuses on the witness's motive or inclination to testify in a slanted way, not on whether the witness has already been caught in a lie. The proponent need not first prove a specific false statement before offering the evidence.
Supporting sources
Is bias impeachment limited to reputation or opinion testimony?+
No. Bias may be proved by any relevant facts, including specific relationships, financial interests, or organizational memberships that give the witness a reason to favor one side. The character-evidence limitations that apply to reputation or opinion do not restrict bias proof.
Supporting sources
Can settlement statements be admitted to show bias?+
Yes. Although compromise offers and related statements are generally inadmissible to prove liability or to impeach by contradiction, the rules expressly permit their use for other purposes such as proving a witness's bias.
Supporting sources
Does religious framing of an organizational loyalty oath bar bias impeachment?+
No. When evidence is offered solely to demonstrate organizational pressure creating bias rather than to attack credibility on the basis of religious belief itself, the inquiry is permissible. Courts may limit the questions to keep the focus on the organizational incentive.
Supporting sources
Proof of bias
is almost always relevant because the jury, as finder of fact and weigher of credibility, has historically been entitled to assess all
evidence
which might bear on the accuracy and truth of…
evidence of bias
before the verdict is rendered, and to employ nonjuror
evidence
even after the verdict is rendered.[^maj-3] IV We further hold, consonant with the Eighth Circuit, that the affidavit…
EvidencePresentation of evidence · Impeachment, contradiction, and rehabilitationUBEIntermediate