In criminal trials, when a regular (non-expert) witness does not like the defendant (and admits it when asked), does that alone give a valid reason to discredit them to any extent at all?

Can the jury be given directions along the lines "this witness does not like the defendant, and that may have been why they testify against him, and hence they may lie"?

On the one hand, it makes perfect sense.

But on the other, if such witnesses were routinely legally discredited, then no victim's testimony would ever be allowed weight.

Where does the balance lie? Are there any rules, principles, tests that are applied to decide whether witnesses disliking defendants are to be believed or not, or to what extent?

Related, but not dupe as it is much broader: Witness credibility questions on cross-examination

3 Answers 3


Only a jury can answer your question, and then on a case-by-case basis.

When a witness testifies, the question of whether and to what extent to believe/disbelieve a witness is nearly 100% the decision of the jury (or the judge in a bench trial).

In a criminal trial, at least, if a thousand disinterested nuns can take the stand and give identical testimony that Defendant robbed the bank, and Defendant's mother says he was actually with her on a Bahamas cruise at the time of the robbery (nevermind the fact that he was arrested exiting the bank), the jury is 100 percent free to conclude the nuns are lying and the mother is telling the truth.

Likewise, if Superman is on trial, the jury would be free to believe or disbelieve whomever they chose if the only evidence they had to rely on was (1) Lex Luthor's testimony that he hates Superman and saw him kill Doctor Light; and (2) Lois Lane's testimony that she loves Superman and saw Lex Luthor do it.

The jury's right to weigh credibility is hundreds of years old.

The question of how to weigh this evidence -- and the answer, which is that it is essentially left entirely to the jury -- is among the most well-settled principles of common-law evidence. See, e.g., Blackstone, Commentaries, 3:354 (1768) ("All others are competent witnesses; though the jury from other circumstances will judge of their credibility.").

Jury instructions therefore routinely advise jurors that they may consider a witness's prejudices for or against the defendant and conclude that his statements are not reliable, whether because he is lying or simply too biased to reliably remember the events in question. United States v. Abel, 469 U.S. 45, 52, 105 S. Ct. 465, 469 (1984) ("Bias is a term used in the 'common law of evidence' to describe the relationship between a party and a witness which might lead the witness to slant, unconsciously or otherwise, his testimony in favor of or against a party. Bias may be induced by a witness' like, dislike, or fear of a party, or by the witness' self-interest.").

You can follow the trail of cases supporting this position quite a ways back. I stopped when I reached Honegger v. Wettstein, 94 N.Y. 252 (1883), a case where a manufacturer sued members of a firm that had bought its goods but never paid. At trial, a principal of the firm testified about the invoiced amount to be paid, and because the testimony was uncontradicted, the judge ordered a directed verdict in favor of the buyers. But the New York Court of Appeals reversed, holding that the credibility of a biased witness's testimony must be left to the jury:

Although not contradicted, he was an interested party, and had a direct interest in increasing the fund in the hands of the receiver, and in preventing its payment to the plaintiffs. His evidence was given for the purpose of showing the alleged violation of law by the plaintiffs, and in explanation of the three invoices which were made of the goods, of which duplicates were made, and it was a fair question for the jury to say whether he might not have been influenced by the circumstances stated.

Ten years later, the Supreme Court addressed your question a bit more directly. In Reagan v. United States, 157 U.S. 301 (1895), a defendant who took the stand was convicted after the trial court told the jury that "Where the witness has a direct personal interest in the result of the suit the temptation is strong to color, pervert, or withhold the facts." But the Supreme Court affirmed the conviction, holding that "the court may, and sometimes ought, to remind the jury that interest creates a motive for false testimony."

Modern courts permit, but do not require, instructions highlighting a specific witness's bias.

These cases of course deal with witnesses who have a bias in favor of a party, but the rule is no different in cases where a witness, as in your question, admits to a bias against a party. In United States v. Coleman, 887 F.2d 266 (6th Cir. 1989), for instance, a defendant was charged with conspiracy to commit arson. Because the only direct evidence of his agreement to the arson was testimony from a witness "who admitted a bias against defendant," he sought a judgment of acquittal, but the trial court denied his motion and sent the case to a jury. The Sixth Circuit affirmed his conviction, holding that it was up to the jury to decide whether the witness was credible:

As defendant points out on appeal, Boscaglia's credibility was very much in issue at trial, but the jury resolved the issue against defendant. The jury's decision on "the credibility of witnesses is not reviewable on appeal."

Although such instructions are allowed, this does not mean that a court is always required to give an instruction addressing the credibility of a specific witness. Depending on who the witness is biased for/against, there are likewise cases saying that no instruction was necessarily required, Kovacich v. Spearman, No. 2:13-cv-0985 KJM DAD P, 2015 U.S. Dist. LEXIS 108233 (E.D. Cal. Aug. 14, 2015) (denying habeas claim by defendant who unsuccessfully sought jury instructions highlighting the bias of the investigating officer), or that such an instruction is a bad idea but not disallowed, United States v. Jones, 372 F. App'x 343, 345 (3d Cir. 2010) ("While such an instruction that singles out the defendant's interest in the case is not advisable, we find that here it did not constitute reversible error.").

I haven't found any saying that such an instruction was a reversible error, though I suspect that there are cases out there in which verdicts were reversed because the judge went overboard in suggesting to a jury how much credibility they should extend an admittedly biased witness.

  • You are missing that provisions such as a judgment notwithstanding the verdict can actually override the jury's conclusion "when the evidence would only allow a reasonable jury to find for the moving party" Marr v. West Corp., 963 N.W.2d 520, 527 (2021). That is likelier to happen if the witness's readily disclosed bias (and as the OP asked: "that alone") is the jury's only reason for discrediting a testimony. Nov 23, 2021 at 17:46
  • No, I'm quite aware of such provisions, and they are routinely applied consistent with my answer and contrary to your interpretation. The court won't grant JNOV (or summary judgment or an MJOP) on that basis because (1) it may not inquire into the jury's rationale for discrediting testimony; and (2) even if it could, biased testimony would in most cases allow a jury to find for either party. Of course, JNOV isn't available in criminal trials, so it's not really relevant to begin with.
    – bdb484
    Nov 23, 2021 at 18:38
  • To make your argument work, you'd have to establish that a witness's bias cannot be discrediting, but I think courts universally reject that argument. Here is the U.S. Supreme Court rejecting it: Reeves v. Sanderson Plumbing Prods., 530 U.S. 133, 150 (2000) ("In entertaining a motion for judgment as a matter of law, the court should review all of the evidence in the record. In doing so, however, the court must draw all reasonable inferences in favor of the nonmoving party, and it may not make credibility determinations or weigh the evidence.").
    – bdb484
    Nov 23, 2021 at 19:01
  • The OP asked whether admission of bias, alone, discredits the witness. U.S. v. Bonilla-Guizar, 729 F.3d 1179, 1186 (2013) explains that bias "is simply another factor the jury may consider in weighing [witness]'s credibility", and then it reinforces my point that admission of bias "may have had the effect of enhancing [witness]'s credibility". "JNOV isn't available in criminal trials, so it's not really relevant to begin with." Don't get too caught up in the term JNOV. Granting a new trial goes in the same direction of a JNOV. Nov 23, 2021 at 20:52
  • These are weird tangents you're chasing down. The question is whether bias can be sufficient to even partially discredit a witness. The answer is yes, but it's a decision for the jury. If you think otherwise, please produce a law saying so.
    – bdb484
    Nov 24, 2021 at 19:11

Partiality may discredit a witness

But that, and the extent to which it discounts their evidence is a matter for the jury.

From the Criminal Trials Bench Book:

[3-625] Motive to lie and the onus of proof

Crown witnesses

  1. A motive to lie or to be untruthful, if it is established, may “substantially affect the assessment of the credibility of the witness”: ss 103, 106(2)(a) Evidence Act 1995. Where there is evidence that a Crown witness has a motive to lie, the jury’s task is to consider that evidence and to determine whether they are nevertheless satisfied that the evidence given is true: South v R [2007] NSWCCA 117 at [42]; MAJW v R [2009] NSWCCA 255 at [31]. The jury’s task does not include speculating whether there is some other reason why the Crown witness would lie: Brown v R [2008] NSWCCA 306 at [50]. Nor does it include acceptance of the Crown witness’s evidence unless some positive answer to that question is given by the accused: South v R at [42].

  2. If the defence case directly asserts a motive to lie on the part of a central Crown witness, the summing-up should contain clear directions on the onus of proof, including a direction that the accused bears no onus to prove a motive to lie and that rejection of the motive asserted does not necessarily justify a conclusion that the evidence of the witness is truthful: Doe v R [2008] NSWCCA 203 at [58]. Where the defence does not directly raise the issue, it is impermissible for the prosecutor to submit (for the purpose of promoting the acceptance of a Crown witness as a witness of truth) that the accused did not advance a motive to lie. The jury should not be given the impression that the accused bears some onus of proving the existence of a motive for the fabrication of the allegations against him or her: Doe v R at [59]–[60].

The accused

  1. It is impermissible to cross-examine an accused to show that he or she does not know of any reason why the complainant (or indeed a central Crown witness) has a motive to lie: Palmer v The Queen (1998) 193 CLR 1 at [8]; Doe v R at [59]. The question focuses the jury’s attention on irrelevant material and invites them to accept the evidence unless some positive answer is given by the accused: Palmer v The Queen at [8]. An open-ended question to the accused, “why would the complainant lie?”, “simply should never be asked” by a prosecutor in a trial: Doe v R at [54]; South v R [2007] NSWCCA 117 at [44]; Causevic v R [2008] NSWCCA 238 at [38]. If in closing addresses the prosecutor makes a comment or asks a rhetorical question to that effect when the issue has not been raised, the judge should give full, firm and clear directions on the onus of proof, including a direction that the accused bears no onus to prove a motive to lie: Palmer v The Queen at [7]–[8]; Doe v R at [59]–[60]; Cusack v R [2009] NSWCCA 155 at [105].

  2. The evidence of an accused person is subject to the tests which are generally applicable to witnesses in a criminal trial: Robinson v The Queen (1991) 180 CLR 531 at 536. However, the trial judge should refrain from directing the jury that the accused’s interest in the outcome of the proceedings is a factor relevant to assessing his or her credibility as a witness: Robinson v The Queen at 535–536; MAJW v R [2009] NSWCCA 255 at [37]–[38]. Robinson v The Queen did not create a new rule. It applied a more general principle that directions should not deflect the jury from its fundamental task of deciding whether the prosecution had proved its case beyond reasonable doubt: Hargraves v The Queen (2011) 245 CLR 257 at [46]. Nevertheless trial judges must not instruct juries in terms of the accused’s interest in the outcome of the proceedings whether as a direction of law or as a judicial comment on the facts: Hargraves v The Queen at [46]. A direction of that kind seriously impairs the fairness of the trial and undermines the presumption of innocence: Robinson v The Queen at 535.

See further Cross-examination of defendant as to credibility at [1-343] and Consciousness of Guilt, Lies and Flight at [2-950]ff.

  • Useful answer, but not on focus, which is when the witnesses themselves confesses of possible motive to lie (e.g. disliking the accused).
    – Greendrake
    Nov 24, 2021 at 2:20

when a regular (non-expert) witness does not like the defendant (and admits it when asked), does that alone give a valid reason to discredit them to any extent at all?

Not alone. It is simply another factor the jury may consider in weighing a witness's credibility. U.S. v. Bonilla-Guizar, 729 F.3d 1179, 1186 (2013).

If anything, from a practical standpoint, the witness's disclosure of bias suggests that his testimony might be more reliable insofar as the witness is prioritizing truthful answers (even those that at the outset might prejudice the testimony altogether) rather than credibility calculations. A transparent disclosure of [dis-]liking the defendant gives the jury a straight-forward element on how much credibility the testimony deserves. The court in Bonilla-Guizar points out that the witness's admission of bias "may have had the effect of enhancing his credibility".

Embry v. State, 923 N.E.2d 1 (2010) addresses evidentiary issues of which the premise is the witness's exposed bias against the defendant. For instance, the opinion points out that "[in] some jurisdictions [...] the State may respond by introducing the defendant's prior uncharged misconduct to explain the witness's antipathy", Id at 7-8. The Embry court took the opposite approach only as to the prior uncharged misconduct, which is short singlehandedly dismissing the witness's testimony.

See also State v. Wacaser, 794 S.W.2d 190, 196 (1990) ("A prosecutor is not necessarily ineligible because he does not like the defendant.").

  • If I disliked the accused so much that I would be lying on the witness stand to hurt them, would I admit to disliking them? Very unlikely.
    – gnasher729
    Nov 23, 2021 at 10:50
  • @gnasher729 If you knew the contents of this answer, maybe you quite would — to boost the credibility of your lies?
    – Greendrake
    Nov 23, 2021 at 12:20
  • This answer is exactly wrong.
    – bdb484
    Nov 23, 2021 at 13:07
  • 1
    @bdb484 Like, even though the witness is truthful about disliking the defendant, they still lie about the rest?
    – Greendrake
    Nov 23, 2021 at 13:29
  • 1
    I think the more likely scenario, though, is that the witness is subconsciously biased in ways that affect his testimony. You're driving and a child darts out in front of you. In your trial for killing her, the prosecution calls a witness who says you were driving too fast and that she has long hated you because you always drive so fast down her street. Wouldn't it be fair to question whether her bias colored her assessment of how you were driving on the day in question? See more in my answer below.
    – bdb484
    Nov 23, 2021 at 16:51

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