FRCP Rule 20 Permissive Joinder

The Two-Part Test for Permissive Joinder

Rule 20(a) sets a two-part test that must be satisfied for permissive joinder of either plaintiffs or defendants. Both elements must be present. First, the claims against or by the joined parties must arise from the same transaction, occurrence, or series of related transactions or occurrences. Second, there must be at least one question of law or fact common to all the joined parties.

The "same transaction or occurrence" test is applied broadly by most courts. It does not require that every claim be identical or that every piece of evidence be shared. It requires a logical relationship between the claims — meaning the claims grow out of the same underlying event, course of conduct, or set of circumstances. A car accident involving multiple vehicles and multiple parties, or a fraud scheme targeting multiple victims, typically satisfies this test.

The "common question" test is even easier to satisfy. One shared legal or factual question is enough. In most multi-party cases, the common question is whether the defendant acted wrongfully at all. If that threshold question applies to all claims, the test is met even if individual damages or circumstances vary from plaintiff to plaintiff.

Rule 20 is permissive, not mandatory. Even when both tests are satisfied, the parties are not required to join. They may file separate actions if they prefer. Permissive joinder is a choice that serves efficiency but is not compelled by the rule itself. Compulsory joinder is governed by Rule 19, not Rule 20.

Joining Multiple Plaintiffs Under Rule 20(a)(1)

Under Rule 20(a)(1), persons may join as plaintiffs if their claims satisfy the two-part test. Multiple plaintiffs who were injured by the same defendant in the same incident — like a workplace accident or a data breach — can typically join under Rule 20 because their claims arise from the same occurrence and share the common question of whether the defendant was negligent or at fault.

Joining multiple plaintiffs creates efficiency for everyone — one set of lawyers, one discovery process, one court. But it also requires coordination. All joined plaintiffs must agree on litigation strategy, discovery positions, and ultimately settlement or trial approach. When plaintiffs have competing interests or different damages profiles, a single joint action can create friction that slows the case down.

One practical note about jurisdiction: in diversity cases, all plaintiffs must be diverse from all defendants. Adding a plaintiff whose citizenship destroys diversity — for example, a plaintiff who is a citizen of the same state as one of the defendants — can eliminate federal jurisdiction for the entire case.

Joining Multiple Defendants Under Rule 20(a)(2)

Under Rule 20(a)(2), persons may be joined as defendants if the claim against each arises from the same transaction or occurrence series and shares a common question. This provision is routinely used in mass tort cases, multi-defendant product liability cases, and cases involving multiple participants in a fraud or conspiracy.

The most common context is a tort case involving joint and several liability. If two defendants acted together to cause a single injury, both can and should be named in the same complaint under Rule 20. If the claims against each defendant are factually independent — arising from separate events at different times with no connection — joinder is improper even if the same legal theory applies to each.

A frequent Rule 20 problem in patent litigation: filing one lawsuit against multiple unrelated defendants for allegedly infringing the same patent. The America Invents Act of 2011 codified prior case law by expressly prohibiting joinder of unrelated defendants in a single patent infringement action solely because they infringe the same patent. Independent infringement of the same patent by separate parties is not a "same transaction or occurrence" under Rule 20.

In contract cases, joining all parties to a multi-party agreement as defendants in one action is generally proper when the dispute concerns interpretation or performance of the agreement, because all claims arise from the same contract and share common legal and factual questions.

Court Authority to Sever or Manage Joined Parties

Permissive joinder under Rule 20 does not guarantee that the case will be tried as one unified action. Rule 20(b) authorizes the court to order separate trials, make other orders to prevent delay or prejudice, or otherwise manage the case to protect the rights of the parties. This gives judges significant flexibility to undo joinder decisions that create unfairness or confusion at trial.

Courts use Rule 42(b) to order separate trials for specific claims or parties when trying everything together would unfairly prejudice one party. For example, in a multi-defendant case where one defendant's prior bad acts are admissible against that defendant but not the others, courts may sever the trials to avoid prejudice from spillover evidence.

From a defense perspective, if you are improperly joined with co-defendants in a case where your conduct has nothing to do with theirs, filing a motion to sever under Rule 21 is the appropriate remedy. Rule 21 specifically allows courts to drop improperly joined parties or sever claims to promote justice and efficiency.

Common Rule 20 Joinder Mistakes

• ✗Joining defendants whose claims have no logical connection: Grouping unrelated defendants in one lawsuit because they used the same product or committed the same type of wrong is not enough — the claims must arise from the same transaction or occurrence.
• ✗Destroying diversity jurisdiction with an improperly joined plaintiff: Adding a plaintiff from the same state as a defendant to share litigation costs can eliminate federal jurisdiction for all plaintiffs.
• ✗Confusing permissive joinder with required joinder: Rule 20 is optional — failing to join a party under Rule 20 does not create a Rule 19 problem unless that party would independently qualify as a required party under the separate Rule 19 analysis.
• ✗Not considering the coordination burden of multiple plaintiffs: Joined plaintiffs must coordinate on all litigation decisions. If their interests diverge significantly, joint representation or joint filing can create as many problems as it solves.

Frequently Asked Questions About Rule 20