Misjoinder Under Rule 8: When Joinder Was Improper From the Start

Misjoinder and Prejudicial Joinder Are Two Different Motions

Two distinct challenges attack a crowded indictment, and confusing them costs defendants. Misjoinder under Rule 8 argues that the charges or defendants never belonged together as a matter of law. Prejudicial joinder under Rule 14 concedes the joinder was technically proper but asks the judge to sever anyway because trying everything together is unfair.

The Fifth Circuit drew the line cleanly in United States v. Laca, 499 F.2d 922 (5th Cir. 1974): “Misjoinder under Rule 8 is an issue of law. In this respect it is unlike prejudicial joinder under Rule 14, which raises only the issue whether the trial judge abused his discretion.” That distinction shapes everything. A misjoinder claim is reviewed as a legal question, so an appellate court gives the trial judge no deference on whether Rule 8 was satisfied. A Rule 14 claim, by contrast, is reviewed only for abuse of discretion, a far harder standard for a defendant to meet.

The practical upshot is that Rule 8 is the stronger argument when it fits, because it does not require proof of prejudice at the outset — only that the indictment exceeded the limits of proper joinder. The two motions are often filed together, with misjoinder as the primary attack and Rule 14 prejudice as the fallback if the court finds joinder technically proper. This satellite focuses on the Rule 8 question; the discretionary prejudice inquiry is covered on the companion pages about antagonistic defenses and spillover prejudice.

The difference is not academic; it changes who has to prove what. On a Rule 8 claim, the defendant points to the four corners of the indictment and argues that the charging decision broke the rule, and no showing of trial prejudice is needed to establish the violation itself. On a Rule 14 claim, the defendant must persuade the trial judge that a technically proper joinder will still be unfair, and then must overcome deferential abuse-of-discretion review on appeal. A defendant with a genuine Rule 8 argument should lead with it, precisely because it does not depend on convincing a court that prejudice is likely.

Rule 8(a): Joining Offenses Against One Defendant

Rule 8(a) governs how many charges the government may stack against a single defendant. It is comparatively generous. Offenses may be joined if they are of the same or similar character, are based on the same act or transaction, or are connected with or constitute parts of a common scheme or plan.

The rule’s text permits an indictment to “charge a defendant in separate counts with 2 or more offenses if the offenses charged — whether felonies or misdemeanors or both — are of the same or similar character, or are based on the same act or transaction, or are connected with or constitute parts of a common scheme or plan.” The “same or similar character” branch is what makes Rule 8(a) broad: the government can try two bank robberies together simply because they resemble each other, even if they are otherwise unrelated. That breadth is precisely why the real protection against unfairness in a single-defendant, multi-count case usually comes from Rule 14 rather than Rule 8. The table below contrasts the two subdivisions.

Rule 8(b): Joining Defendants in the Same Series

Rule 8(b) is narrower than 8(a), and deliberately so. Two or more defendants may be joined only if they are alleged to have participated in the same act or transaction, or in the same series of acts or transactions, constituting an offense or offenses. There is no “same or similar character” option for joining people.

The Fifth Circuit has defined the operative phrase. In United States v. Marionneaux, 514 F.2d 1244 (5th Cir. 1975), the court explained that to be joined under Rule 8(b), defendants “must be alleged to have participated (1) in the same act or transaction or (2) in the same series of acts or transactions constituting an offense or offenses,” and that the “same or similar character” basis from 8(a) is simply not a permissible ground for joining defendants. A “series” requires a “substantial identity of facts or participants” between the offenses.

Marionneaux applied that test to two conspiracies charged in one indictment. Because there was “no substantial identity of facts or participants between the two offenses,” the court held there was “no ‘series’ of acts under Rule 8(b),” and the defendants were misjoined. The lesson is important: a single common defendant, or a shared general goal, does not turn separate schemes into one series. The government must allege facts showing the defendants were genuinely tied into the same overarching course of conduct, not merely that their crimes looked alike or happened around the same time.

The Marionneaux facts make the point concrete. The indictment charged two separate conspiracies to obstruct justice, and the government pointed to a common participant and a shared general goal to tie them together. The court found that insufficient: overlapping objectives and one shared defendant did not create the “substantial identity of facts or participants” that a single series demands, because the overt acts and the other participants differed. The result was reversal and an order for separate trials. The case is a reminder that Rule 8(b) asks about genuine factual interconnection, not thematic similarity, when the government joins defendants.

When Multiple Defendants Are Charged, Rule 8(b) Controls

A recurring mistake is to defend a multi-defendant indictment as if Rule 8(a) applied to the counts. It does not. Once there is more than one defendant, Rule 8(b) governs the joinder of both the defendants and the offenses, and the more permissive 8(a) standard drops out entirely.

Laca stated the rule directly: “Whether there has been a misjoinder in a trial involving multiple defendants is governed by Rule 8(b); Rule 8(a) has no application in such instances.” That single sentence decides many cases. If the government tries to justify joining defendants by pointing to offenses of a “similar character,” the argument fails, because that basis exists only in 8(a), which no longer applies. The prosecution must instead show a shared act, transaction, or series.

Rule 8(b) also answers a common defense objection that is not actually a misjoinder. The rule expressly allows defendants to be “charged in one or more counts together or separately,” and provides that “all defendants need not be charged in each count.” As Laca recognized, “there is no misjoinder simply because one defendant is not charged in each count of the indictment.” A defendant who appears in only two of ten counts is not misjoined for that reason alone, so long as everyone is tied into the same series of acts or transactions. The correct question is always whether the connective tissue Rule 8(b) demands is present, not how many counts name each person.

This is also why conspiracy charges loom so large in multi-defendant indictments. A properly pleaded conspiracy count alleges, on its face, that the defendants participated together in a single series of acts, which is exactly what Rule 8(b) requires. Prosecutors routinely use a conspiracy count as the hub that makes joinder of otherwise diverse substantive counts proper. For the defense, that means a misjoinder challenge often has to start by testing the conspiracy allegation itself — whether the indictment really alleges one shared agreement, or instead lumps together separate ventures that happen to involve some of the same people.

Misjoinder Is Judged on the Face of the Indictment

Because misjoinder is a legal question about how the case was charged, courts decide it by reading the indictment, not by weighing the trial evidence. What the government alleges controls, and those allegations are taken as true for purposes of the motion.

The Fifth Circuit stated the standard in United States v. Faulkner, 17 F.3d 745 (5th Cir. 1994): “The propriety of joinder under Rule 8 is determined on the basis of the allegations in the indictment, which are accepted as true barring allegations of prosecutorial misconduct.” The court also observed that “proof of such a common scheme is typically supplied by an overarching conspiracy from which stems each of the substantive counts.” A conspiracy count is often the thread that makes joinder proper, because it alleges the shared series of acts that ties the defendants together.

This face-of-the-indictment rule cuts both ways. It means the defense cannot defeat joinder merely by showing the trial proof turned out weak; if the indictment properly alleged a series, joinder was proper when made. But it also means the government cannot save a facially defective indictment with evidence it develops later. Faulkner added the sequencing point that matters for strategy: “If joinder is proper in the first instance under Rule 8, the denial of a motion for severance is reviewable only for an abuse of discretion.” In other words, once Rule 8 is satisfied, the defendant is pushed back into the harder Rule 14 world.

The Remedy and the Harmless-Error Trap of Lane

For decades, misjoinder carried a powerful remedy. Fifth Circuit cases such as Marionneaux described improper joinder under Rule 8 as “inherently prejudicial,” making severance mandatory and treating misjoinder as reversible almost automatically. The Supreme Court changed that in 1986, and defendants must account for the shift.

In United States v. Lane, 474 U.S. 438 (1986), the Court held that “an error involving misjoinder affects substantial rights and requires reversal only if the misjoinder results in actual prejudice because it had substantial and injurious effect or influence in determining the jury’s verdict.” Misjoinder is now subject to harmless-error analysis under the Kotteakos standard. Lane also clarified that “improper joinder does not, in itself, violate the Constitution” and rises to a due-process violation only where the prejudice is so great as to deny a fair trial.

Lane creates a trap for the unwary. A defendant can be entirely correct that Rule 8 was violated and still lose the appeal if the reviewing court concludes the misjoinder did not sway the verdict. That reality drives two practical points. First, raise the misjoinder objection before trial under Rule 12(b)(3)(B)(iv), which requires a claim of improper joinder to be made by pretrial motion, so the issue is preserved on the strongest footing. Second, build a concrete record of how the improper joinder actually harmed the defense — evidence the jury heard that it never would have in a proper trial — because after Lane, showing that harm is what turns a technical misjoinder into a reversal.

The harmless-error standard Lane borrowed from Kotteakos is not the same as asking whether the evidence was sufficient to convict. The question is whether the misjoinder itself — the fact that the jury heard the counts or codefendants together — had a substantial and injurious effect on the verdict. Overwhelming evidence of guilt makes a finding of harmlessness more likely, but it is not the test. That distinction gives the defense its opening: by isolating specific evidence the jury would never have encountered in a properly separated trial, and showing how it likely shaped the outcome, counsel can meet the actual-prejudice standard even when the overall proof was strong.

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.

• United States v. Lane, 474 U.S. 438 (1986) — Misjoinder under Rule 8 is subject to harmless-error review and requires reversal only if it had a substantial and injurious effect on the verdict.
• United States v. Laca, 499 F.2d 922 (5th Cir. 1974) — Misjoinder under Rule 8 is an issue of law, unlike Rule 14 prejudice; in a multi-defendant case Rule 8(b) governs and 8(a) does not apply.
• United States v. Marionneaux, 514 F.2d 1244 (5th Cir. 1975) — Two separate conspiracies with no substantial identity of facts or participants are not a single series under Rule 8(b); the defendants are misjoined.
• United States v. Faulkner, 17 F.3d 745 (5th Cir. 1994) — The propriety of joinder under Rule 8 is judged on the allegations of the indictment, accepted as true absent prosecutorial misconduct.

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