Mutually Antagonistic Defenses and Severance

What Makes Codefendant Defenses Mutually Antagonistic?

Defenses become mutually antagonistic when codefendants do not merely disagree but blame each other in ways that cannot both be true. The classic case is finger-pointing: each defendant tells the jury that the other is the guilty one, so accepting one story requires rejecting the other. Mere friction is not enough.

The Fifth Circuit set the standard in United States v. Berkowitz, 662 F.2d 1127 (5th Cir. Unit B 1981). The court held that a defense “reaches a level of antagonism that compels severance . . . if the jury, in order to believe the core of testimony offered on behalf of that defendant, must necessarily disbelieve the testimony offered on behalf of his co-defendant.” When that happens, the court warned, “the co-defendants do indeed become the government’s best witnesses against each other.” The danger is that the jury will “unjustifiably infer that this conflict alone demonstrates that both are guilty.”

Berkowitz also fixed the threshold: “to compel severance the defenses must be more than merely antagonistic — they must be antagonistic to the point of being mutually exclusive” or “irreconcilable.” A defendant who simply thinks his odds improve without a codefendant in the room has shown nothing. The conflict must sit at the essence of the two defenses, so that one truly preempts the other, before it even begins to matter for severance.

Zafiro: Antagonistic Defenses Are Not Prejudicial Per Se

Even a genuine, irreconcilable conflict does not guarantee separate trials. The Supreme Court made that clear in the decision that now controls every federal severance motion built on clashing defenses. Antagonism is a factor, not a trump card.

In Zafiro v. United States, 506 U.S. 534 (1993), the Court squarely held that “mutually antagonistic defenses are not prejudicial per se” and that “Rule 14 does not require severance even if prejudice is shown; rather, it leaves the tailoring of the relief to be granted, if any, to the district court’s sound discretion.” The Court then supplied the operative test: “a district court should grant a severance under Rule 14 only if there is a serious risk that a joint trial would compromise a specific trial right of one of the defendants, or prevent the jury from making a reliable judgment about guilt or innocence.”

Two consequences follow. First, the mere fact that codefendants accuse each other is not, by itself, a reason to sever. Second, even where real prejudice exists, severance is only one possible response. The Court pointed to “less drastic measures, such as limiting instructions,” which “often will suffice to cure any risk of prejudice.” Zafiro also reaffirmed the baseline that “defendants are not entitled to severance merely because they may have a better chance of acquittal in separate trials.” The Rule 14 question is about the reliability and fairness of the joint trial, not the tactical comfort of the accused.

Core Conflict Versus Peripheral Conflict

The severance analysis lives or dies on whether the clash touches the heart of each defense or only its edges. Courts distinguish sharply between conflict at the core — where one defense cannot be true unless the other is false — and disagreement over collateral details that a jury can accept without convicting anyone.

Berkowitz drew the line: “compelling prejudice does not arise with respect to a defendant where the conflict concerns only minor or peripheral matters which are not at the core of his defense.” If the essence of one defendant’s defense is contradicted by the codefendant’s, the second defense can be said to “preempt” the first, and that is the situation the rule addresses. Where the defenses can coexist — for example, two defendants who each say they did not know what was in a package, a scenario the concurrence in Zafiro flagged — acceptance of one does not require rejection of the other, and there is no true antagonism. The table below illustrates the difference.

A Concrete Example: Romanello

A pre-Zafiro Fifth Circuit case shows what a genuinely mutually exclusive conflict looks like and how it can arise even from the words of counsel rather than the defendant’s own testimony. It remains a useful illustration of the kind of core conflict the doctrine targets.

In United States v. Romanello, 726 F.2d 173 (5th Cir. 1984), one defendant claimed he had been robbed of gold; the other defendants claimed they were innocent shippers who had merely been hired to drive it. As the court put it, if the jury believed the two defendants robbed the first, “then it could not believe that they were innocent shippers,” and vice versa. The defenses were “irreconcilable and mutually exclusive.” The court also held that the accusation could come from an attorney: an accusation made by a codefendant’s counsel in opening statement and throughout trial “is sufficient to create an antagonistic defense,” and severance may be required “if only one defendant accuses the other, and the other denies any involvement.”

Romanello distilled the situation into a checklist: a defendant may be entitled to a severed trial when the core of his defense is the guilt of his codefendant, disproving his defense would establish his own guilt, the two defenses are irreconcilable and mutually exclusive, the codefendant actively attacks his defense at trial, and he suffers compelling prejudice as a result. That framework survives Zafiro as a way to identify true antagonism, though after Zafiro even a defendant who satisfies it must still show the serious risk to a trial right or a reliable verdict that Rule 14 now requires.

Why Most Antagonism Does Not Win Severance

In practice, motions to sever based on antagonistic defenses fail far more often than they succeed. The reason is the gap between the strong preference for joint trials and the demanding showing Zafiro requires. Understanding that gap keeps expectations realistic.

The Fifth Circuit synthesized the modern rule in United States v. Daniels, 281 F.3d 168 (5th Cir. 2002). The court described its own necessarily-disbelieve standard as “stringent,” requiring defenses “so diametrically opposed” that believing one core defense means disbelieving the other, and emphasized that after Zafiro “the federal system prefers joint trials of defendants who are properly charged in joint indictments.” To prevail, a defendant must show “that the joint trial prejudiced him to such an extent that the district court could not provide adequate protection” and that the prejudice “outweighed the government’s interest in economy of judicial administration.”

That is a heavy load. Trial judges routinely respond to clashing defenses with firm instructions telling jurors to consider each defendant separately and to treat arguments of counsel as argument, not evidence. Because courts presume juries follow such instructions, the availability of that lesser remedy usually defeats the argument that only severance can protect the defendant. The winning motions tend to involve something extra — a defense that cannot be presented at all without a separate trial, evidence admissible against one defendant that would never reach the other alone, or a conflict so central that no instruction can neutralize it.

How to Present an Antagonistic-Defense Severance Motion

Because the standard is demanding, the motion has to be specific, well-timed, and preserved. General complaints that codefendants “don’t get along” go nowhere; the court needs to see exactly how the joint trial threatens a concrete right or a reliable verdict.

The request is a pretrial motion under Rule 12(b)(3)(D), which requires a motion to sever defendants under Rule 14 to be raised before trial when the basis is reasonably available. A strong motion identifies the specific defense the client intends to present, explains why it is irreconcilable with a codefendant’s defense at its core rather than at the margins, and shows why a limiting instruction cannot cure the resulting prejudice — the exact point Zafiro says courts will test first. Framing the harm in Zafiro’s own terms, as a serious risk to a specific trial right or to the jury’s ability to render a reliable judgment, matters, because that is the language the court must apply.

Preservation continues through trial. As Berkowitz recognized, the district court “has a continuing duty to monitor the entire trial for prejudice and to order severance if such prejudice does arise.” Antagonism that was only theoretical before trial can become concrete once the codefendants actually testify and attack each other, so counsel should renew the motion when the conflict materializes. Making a fresh record at that point both gives the trial judge a chance to grant relief and preserves the strongest version of the issue for any appeal.

Where This Fits

This guide is one of four situations that arise under the Motion to Sever Defendants or Counts. Start with the parent motion for the overall framework, or move to a related fact pattern:

What the Case Law Says

These decisions—verified against primary sources—control how this issue is litigated. Every case still turns on its own facts.

• Zafiro v. United States, 506 U.S. 534 (1993) — Mutually antagonistic defenses are not prejudicial per se; Rule 14 severance is discretionary and requires a serious risk to a specific trial right.
• United States v. Berkowitz, 662 F.2d 1127 (5th Cir. Unit B 1981) — Defenses are antagonistic enough to matter only if, to believe the core of one defendant's testimony, the jury must necessarily disbelieve the codefendant's.
• United States v. Romanello, 726 F.2d 173 (5th Cir. 1984) — Defenses were irreconcilable where some defendants claimed to be innocent shippers and another claimed robbery; an accusation by codefendant counsel can create antagonism.
• United States v. Daniels, 281 F.3d 168 (5th Cir. 2002) — The necessarily-disbelieve standard is stringent and, after Zafiro, severance is an exception given the federal preference for joint trials.

General summaries of published opinions for information only — not predictions about any specific case.