FRCP Rule 21 Misjoinder Guide

The Core Rule: Misjoinder Is Not Grounds for Dismissal

Rule 21 opens with a foundational principle: misjoinder of parties is not a ground for dismissing an action. This is an intentional departure from the old common law approach, which sometimes required dismissal when the wrong parties were included. Under Rule 21, the remedy for misjoinder is severance or dropping — not terminating the case.

On motion or on its own initiative, the court may at any time add a party, drop a party, or sever any claim against a party. The rule gives courts broad and flexible authority to correct party structure problems whenever they arise — at the pleading stage, during discovery, or even at trial. Courts also have authority to order a party dropped from the case sua sponte if joinder would deprive the court of subject matter jurisdiction.

The power to drop parties is frequently used in diversity jurisdiction cases. When a plaintiff joins a non-diverse party whose citizenship destroys complete diversity, but that party is not essential to the case, the court can drop the non-diverse party to preserve federal jurisdiction. Courts must analyze whether the dropped party is indispensable under Rule 19 before making this decision.

What Misjoinder Means in Practice

Misjoinder occurs when a party is joined in violation of the applicable joinder rules — most commonly Rule 20's requirement that joined parties' claims arise from the same transaction or occurrence and share a common question. If the claims against two defendants are factually unrelated — separate incidents, separate damages, no common conduct — those defendants are misjoined even if the same legal theory applies to each.

Patent infringement cases illustrate this clearly. After the America Invents Act, courts routinely sever patent infringement claims against defendants who are accused of independently infringing the same patent without any connection to each other. Each defendant's infringement is a separate occurrence, making multi-defendant patent cases classic misjoinder situations under Rule 21.

Misjoinder can also occur when a plaintiff adds a defendant simply because they are a convenient target or available insurer, rather than because they have any connection to the transaction giving rise to the claims. Courts look at the factual and legal connection between all joined parties when evaluating a misjoinder challenge.

Severance Under Rule 21: Creating Independent Cases

When a court severs claims under Rule 21, it creates separate and independent actions. This is different from bifurcation under Rule 42(b), which divides a single action into phases that still result in one judgment. Severance under Rule 21 produces two separate cases with separate docket numbers, separate discovery tracks, and separate judgments.

One critical consequence of severance: statutes of limitations. When claims are severed under Rule 21, the severed action is typically treated as filed on the date the original complaint was filed — not on the date of severance. This protects plaintiffs from having their newly independent claims time-barred because severance happened after the limitations period would have run. Courts have consistently held that Rule 21 severance preserves the original filing date for limitations purposes.

Defendants sometimes request severance to simplify a complex multi-party case. A defendant who has been improperly bundled with other defendants whose conduct is unrelated to theirs may move for severance to focus the litigation on claims that are actually directed at them, rather than sitting through discovery and trial testimony about co-defendants with no connection to their case.

Courts weigh judicial economy against fairness when considering severance requests. Severance adds case load — two cases instead of one. But trying improperly joined claims together can confuse juries and create unfair prejudice from spillover evidence. Courts generally grant severance when the factual connection between the joined claims is minimal and the risk of prejudice is real.

Adding Parties Under Rule 21

Rule 21 also authorizes courts to add parties to an action on motion or sua sponte. This power overlaps with the amendment provisions of Rule 15 and the required party joinder provisions of Rule 19. Courts use Rule 21 to add parties when the case structure reveals that an essential person has been omitted and joinder is feasible.

The authority to add parties under Rule 21 is broader than Rule 19 in one sense — it does not require that the added party be "required" in the Rule 19 sense. Courts can add parties under Rule 21 whenever justice and efficiency require it, even for permissive purposes. However, adding a party who is not required and has not moved to intervene requires careful analysis of jurisdiction and Rule 20 joinder standards.

When the court adds a party under Rule 21 after the statute of limitations has run, the relation-back doctrine under Rule 15(c) may apply if the new party had notice of the action within the service period. Courts analyze this on a case-by-case basis using the same factors as for amendments adding new defendants under Rule 15(c)(1)(C).

Rule 21 and Jurisdiction Preservation

One of Rule 21's most important applications is preserving diversity jurisdiction by dropping non-diverse parties. In a diversity case, if a plaintiff joins a defendant who is a citizen of the same state as the plaintiff — destroying complete diversity — but that defendant is not a required party under Rule 19, the court may drop the non-diverse defendant to restore complete diversity and retain federal jurisdiction.

This maneuver is also used in reverse. Defendants in state court sometimes argue that a plaintiff improperly joined a non-diverse defendant solely to defeat removal to federal court. Under the "fraudulent joinder" doctrine, courts can disregard the citizenship of a party joined without any plausible claim, and if the remaining parties are diverse, the case can be removed. Rule 21 then provides the mechanism to formally drop the fraudulently joined party after removal.

Common Rule 21 Mistakes

• ✗Treating severance and bifurcation as the same thing: Severance under Rule 21 creates separate independent cases. Bifurcation under Rule 42(b) just separates phases of one case. The consequences for deadlines and appeals are completely different.
• ✗Not considering statute of limitations when requesting severance: Before moving for severance, calculate whether the severed claim would be time-barred on its own. Understanding the relation-back protection of Rule 21 severance is essential.
• ✗Filing a misjoinder motion without addressing Rule 19: When asking the court to drop a party, you must address whether that party is required under Rule 19. If they are, dropping them may require dismissal of the entire action rather than just severance.
• ✗Waiting too long to raise misjoinder: While misjoinder is not technically waived in the same way as other defenses, courts look unfavorably on late-raised misjoinder arguments, especially after extensive shared discovery has already been completed.

Frequently Asked Questions About Rule 21