The Two Requirements

The Two Requirements

Rule 20(a)(1) permits plaintiffs to join only when their case satisfies two conditions at once. Under subparagraph (A), the plaintiffs must assert a right to relief, jointly, severally, or in the alternative, with respect to or arising out of the same transaction, occurrence, or series of transactions or occurrences.¹ Under subparagraph (B), some question of law or fact common to all plaintiffs must arise in the action.² The rule links the two with and, and courts treat the tests as cumulative: a joinder that satisfies one test and fails the other is improper.³

The tests ask different questions. The first looks to the factual origin of the claims and asks whether they are connected closely enough to belong in one case. The second looks to what the court will decide and asks whether some issue reaches every plaintiff. The court in Smith v. North American Rockwell Corp. put the point plainly: the rule states two requirements for proper joinder, and both must be satisfied.⁴

Neither test comes with a bright-line definition. The joinder provisions are very broad, and the court may order separate trials or make other orders to prevent delay or prejudice. The scope of a civil action thus becomes a matter for the judge's discretion, decided on practical considerations in the particular case rather than by the conceptual tests that governed at common law and under some of the codes.⁵ Joinder disputes therefore turn on how closely the plaintiffs' facts and issues overlap.

Same Transaction or Occurrence

Subparagraph (A) asks whether the plaintiffs' claims grow out of the same events, and courts answer case by case. In Mosley v. General Motors Corp., ten employees sued their employer and its union, and the court explained that no hard and fast rules define a single transaction or occurrence.⁶

The working guide comes from the compulsory-counterclaim rule, which uses the same words. Rule 13(a) requires a party to plead, in the same action, any counterclaim that arises out of the same transaction or occurrence as the opposing party's claims, and a party who does not risks losing it; counterclaims that do not arise from that transaction or occurrence are permissive.⁷ Courts applying Rule 20 borrow the logical-relationship test developed under that provision. The test began as a judicial gloss on the transaction-or-occurrence standard in the federal equity rules, and it defines the relationship in terms of judicial economy and convenience: parties may be joined when enough of the facts overlap that litigating together is efficient.⁸ Under the counterclaim decisions, which include Moore v. New York Cotton Exchange, logically related events that entitle a person to sue another generally comprise one transaction or occurrence. Carried into Rule 20, that reading permits all reasonably related claims by or against different parties to be tried in one proceeding, and absolute identity of all events is unnecessary.⁹

Rule 20's text also goes beyond Rule 13(a)'s, because it adds “series of transactions or occurrences,” words Rule 13(a) lacks.¹⁰ Mosley shows what the added words can do. Each of the ten plaintiffs alleged injury from the same general policy of discrimination by General Motors and the union. The court observed that a state-wide system for enforcing registration laws so as to deprive Black citizens of the vote had been held to arise out of the same series of transactions or occurrences, and it concluded that a company-wide policy designed to discriminate against Black employees arises out of the same series, so the plaintiffs met the first requirement.¹¹ Later sections on policy and pattern claims return to this reasoning.

Ordinary tort cases show how much separation a series can absorb. A passenger whose car was struck in the rear twice in one day, once on the way to work and once on the way home, was allowed to join both other drivers in one action. In a similar case, the second defendant's conduct did not occur until 18 days after the original injury, yet the court permitted joinder of both defendants. The apparent separateness of the torts gave way because, under the applicable substantive law, the first tortfeasor could be held liable for the total injury in both cases.¹² The overlap can also run too thin. Three former smokers sued cigarette manufacturers and trade organizations for fraud and conspiracy to conceal the health effects of smoking. Although each alleged an industry-wide conspiracy, a court refused joinder because the facts tied to each smoker threatened jury confusion and prejudice to the defendants.¹³

A shared defendant or a shared legal theory therefore does not by itself supply a transaction. In Smith, the court held that a general notion that promotions had been denied in at least three cases could not support joinder, because different supervisors, in different labor union and work environments, would have made the decisions about employees doing different types of work.¹⁴ The same holds when the only link is a legal question. A bank cannot sue all of its debtors on promissory notes in one action by pointing to a common question of law, because joinder is not permitted unless the notes involve a single transaction or series of transactions.¹⁵ The converse also holds. The test is one of historically related events, so claims based on different legal theories, or on different sources of law such as one state claim and one federal claim, can still satisfy it.¹⁶

Treating “transaction” and “occurrence” as separate hurdles invites hairsplitting. In one case, plaintiffs sought to join a claim against the persons who set off dynamite, causing an explosion, with a claim against the insurers of the damaged property, and whether the explosion or some other cause did the damage was a question of fact common to all the defendants. The court nevertheless refused joinder, reasoning that the dynamiting was an “occurrence” and the insurance a “transaction,” so the claims arose from neither a single transaction nor a single occurrence.¹⁷ A leading commentary calls that an undesirable overrefinement. The sounder inquiry asks one question, whether the claims are logically related, whichever label the events fit.

Courts reduce the inquiry to a practical measure. One district court asked whether there are “enough ultimate factual concurrences that it would be fair to the parties to require them to defend jointly” against the several claims.¹⁸ In Hall v. E.I. Du Pont De Nemours & Co., plaintiffs injured in separate blasting-cap accidents sued the manufacturers. The court found it neither fair nor convenient to try the facts of every accident in one forum, yet unfair and burdensome to make each plaintiff prove the alleged joint activities in ten separate, repetitive actions.¹⁹ It let the plaintiffs litigate the joint-activity issues together, because their right to relief rested to a significant but not complete extent on alleged joint activity, and it transferred the questions that turn on each accident to the districts where the accidents occurred.²⁰ As one opinion collecting the decisions observed, courts incline toward finding a single transaction or occurrence when overlapping proof and duplicated testimony mean that separate trials would add delay, inconvenience, and expense.²¹

Common Question of Law or Fact

Rule 20(a)(1)(B) requires that “any question of law or fact common to all plaintiffs” will arise in the action.²⁴ The word any means one shared question is enough. Mosley confirms the point: the rule does not require that all questions of law and fact raised by the dispute be common, although it sets no qualitative or quantitative test of how much commonality suffices. Because Rule 23(a) contains a parallel requirement, the court found the cases construing that rule a helpful framework.²⁵ The phrase common to all means the question must reach every plaintiff, and will arise in the action ties the test to issues the litigation will actually present.

The threshold is low because modern joinder doctrine rejects the absolutism of the early codes. Overlapping interests are still required, but the overlap can be less than total.²⁶ The examples show how much individual variation a common question can absorb. In a New York case construing a statute on which Rule 20 was based, 193 persons who each had been induced by a fraudulent prospectus to invest in a sham corporation joined in one fraud action against the promoters. Whether the prospectus was fraudulent justified joinder even though each plaintiff would still have to show that he or she saw the prospectus and relied on it. Automobile-collision plaintiffs commonly join because the defendant's negligence is common to all of them, although damages and contributory negligence vary. And in a suit against an employer for discrimination, the discriminatory character of the employer's conduct is common to all plaintiffs even though particular plaintiffs suffered different effects.²⁷

A common question of fact can carry the joinder alone. In Hall v. E.I. Du Pont De Nemours & Co., the blasting-cap plaintiffs' claims raised common questions of fact, such as whether the defendants exercised joint control over the labeling of blasting caps and operated as a joint enterprise, for purposes of tort liability, with respect to that labeling. The court stressed the disjunctive: the rule requires only “any question of law or fact common to all” the plaintiffs.²⁸ Environmental claims work the same way. When a chemical plant's discharge injures several neighbors, whether the chemicals came from the plant and whether their amount exceeded permissible limits are questions common to all the claims, and litigating them together gains efficiency even though other issues, such as each farmer's crop losses, differ.²⁹

The common question must still be real. An inconsequential or theoretical issue common to all the plaintiffs will not permit joinder. In the words of the New York Court of Appeals, “such common questions must be of substantial importance as compared with all of the issues,” and the comparative weight of common and separate issues is largely a matter of judgment.³⁰

Two employment cases mark the line between a real common question and an empty one. In Mosley, the court held that the discriminatory character of the defendants' conduct was basic to each plaintiff's recovery, so each plaintiff's right to relief depended on showing that the same racially discriminatory policies had wronged him.³¹ In Smith, a general notion of promotion denials could not support joinder where different supervisors made the decisions in different work environments.³² The difference lies in whether one decision by the defendant is alleged to stand behind every claim. A single policy, once proved for one plaintiff, is proved for all, while separate supervisors' decisions tell the court nothing about the next claim.

Differences in what each plaintiff suffered do not defeat commonality, because the question that matters is whether the defendant's conduct is basic to every recovery. Mosley reasoned that when the discriminatory character of the defendants' conduct is basic to each plaintiff's recovery, the fact that each plaintiff suffered different effects is immaterial to the common question. The court held that the trial court abused its discretion in severing the joined actions, because the difficulty of adjudicating individual damages was not so overwhelming as to require severance, and it noted that separate trials remain available if appropriate.³³

Commonality never replaces the transaction requirement. Some early decisions read “question of law” to cover only legal questions arising from the facts of the particular case, not general principles of law, in order to stop a bank from suing every debtor on promissory notes by invoking a common legal question. That worry overlooks that joinder would fail anyway unless the notes involved a single transaction or series of transactions.³⁴ The tests are cumulative, so a substantial shared question cannot rescue claims that grow out of unrelated events.³⁵ One question about the common-question test remains open. Mosley looked to the cases under Rule 23(a), and in 2011 the Supreme Court narrowed the meaning of the parallel class-action requirement in Wal-Mart Stores, Inc. v. Dukes, requiring a common question whose determination will resolve an issue central to the validity of each claim in one stroke. Whether that narrower reading should carry over to Rule 20 is unsettled.³⁶