Joinder of claims, parties and intervention

One Action or Several: Match the Party Relationship to the Joinder Device

The Federal Rules separate claim joinder, which combines legal claims, from party joinder, which brings additional plaintiffs or defendants into the action. The analysis therefore begins by asking whether the proposed addition is another claim against an existing opponent or a new person whose participation must independently satisfy a joinder rule.

Rule 18 governs multiple claims against an opposing party. Once a party has a proper procedural foothold in the action, that party may join as many claims as it has against the opposing party, whether or not the claims arise from the same transaction or share facts. Rule 18 does not itself authorize adding a new person. Each additional claim must fall within original or supplemental subject-matter jurisdiction. Unrelated claims generally do not fall within supplemental jurisdiction.

Rule 20 governs permissive joinder of parties. A plaintiff may join plaintiffs, or a plaintiff may sue defendants together, only when both requirements are met:

The claims arise out of the same transaction, occurrence, or series of transactions or occurrences; and
The claims present at least one common question of law or fact.

For defendants, the relief must be asserted against them jointly, severally, or in the alternative. For plaintiffs, the right to relief must likewise be asserted jointly, severally, or alternatively. A common legal issue by itself is not enough; the transaction-or-occurrence connection is also required. Conversely, identical claims and identical relief are unnecessary. Once parties are properly joined under Rule 20, Rule 18 permits additional claims against an opposing party, even unrelated ones, subject to jurisdiction.

Device	Required connection	What it adds	Main consequence
Rule 18	No transaction connection required	Additional claims against an existing opponent	All claims may be joined, but jurisdiction remains necessary
Rule 20	Same transaction or occurrence plus common law or fact question	Plaintiffs or defendants	Permissive party joinder; court may later sever
Rule 13(g)	Same transaction or occurrence, or property involved in the action	Claim against a co-party	Crossclaim is permitted, not generally compulsory
Rule 14	Nonparty may owe defending party all or part of plaintiff’s claim	Third-party defendant	Impleader creates derivative liability practice

The jurisdictional checkpoint matters. Joinder under the Federal Rules does not create subject-matter jurisdiction, personal jurisdiction, or venue. Under 28 U.S.C. § 1367(a), supplemental jurisdiction may cover additional claims forming part of the same Article III case or controversy. But when original jurisdiction rests solely on diversity, § 1367(b) restricts certain claims by plaintiffs against persons joined under Rules 14, 19, 20, or 24, and certain claims by persons seeking to join as plaintiffs under Rules 19 or 24. Thus, a fact pattern may show proper Rule 20 joinder but still require dismissal of a particular claim for lack of jurisdiction.

A counterclaim is a claim by a party against an opposing party. Under Rule 13(a), a counterclaim is compulsory when, at the time the pleading is served:

It arises out of the transaction or occurrence that is the subject matter of the opposing party’s claim; and
It does not require adding another party over whom the court cannot acquire jurisdiction.

The pleader generally must state the compulsory counterclaim in the pending action or risk losing it in a later action. Rule 13(a) supplies limited exceptions, including when the claim was already the subject of another pending action when the federal action began. A claim that does not meet Rule 13(a) is a permissive counterclaim under Rule 13(b). It may be asserted, but it must have its own jurisdictional basis or qualify for supplemental jurisdiction. The near miss is important: “related” is not the same as “compulsory”; the transaction-or-occurrence connection and the jurisdictional condition must both be present.

A crossclaim is different because it is asserted against a co-party, not an opposing party. Under Rule 13(g), a crossclaim is permitted when it arises out of the transaction or occurrence that is the subject matter of the original action or of a counterclaim, or when it relates to property that is the subject matter of the original action. Crossclaims are generally permissive, not compulsory. A defendant’s claim against a codefendant is therefore a crossclaim, even if it arises from the same accident that generated the plaintiff’s claim; calling it a counterclaim changes the applicable rule.

This is closed-book: you must be able to state these requirements from memory.

The Court’s Brake Pedal: Cure Misjoinder or Separate the Trial

A court’s power to control joinder is broader than the parties’ initial pleading choices. Under Rule 21, misjoinder is not a ground for dismissing an entire action. Instead, on motion or on its own, the court may at any time, on just terms, add or drop a party. The court may also sever any claim against a party. The usual point is to cure an improper combination without destroying otherwise valid claims.

The court may also sever even when joinder was proper. Rule 20’s requirements answer whether parties may initially proceed together; they do not guarantee a joint trial. A court may separate claims or parties when trying them together would create confusion, prejudice, delay, or inefficient presentation.

Keep two consequences separate:

Rule 21 severance separates a claim into a distinct action. The severed claim continues; severance is not a merits dismissal.
Rule 42(b) separate trials separates the trial of claims or issues while leaving them within the same action. It is a case-management device, not necessarily the creation of a new lawsuit.

The court’s overriding power is therefore a second-stage inquiry: first ask whether the joinder device was authorized; then ask whether practical considerations justify severance or separate trials. A party cannot defeat severance by showing that Rule 20 was technically satisfied, and a court cannot dismiss the whole case merely by labeling joinder “misjoinder.”

Third-party practice illustrates both joinder and judicial control. Under Rule 14(a)(1), a defending party may serve a third-party complaint on a nonparty who is or may be liable to the defending party for all or part of the plaintiff’s claim. This is derivative liability: indemnity, contribution, or another obligation contingent on the defending party’s liability. A defendant may not use Rule 14 merely to assert that a nonparty independently injured the plaintiff. That is a direct-liability theory, not impleader.

The timing is a frequent separator. A defending party may serve the third-party complaint without leave within 14 days after serving its original answer. After that period, court permission is required. The third-party defendant may assert defenses against the third-party plaintiff’s claim and may assert claims against the third-party plaintiff arising from the same transaction or occurrence. The original plaintiff may assert against the third-party defendant a claim arising from the same transaction or occurrence, and the third-party defendant may respond with a corresponding claim against the original plaintiff. The court may strike, sever, or try separately any such claim.

Thus, when a defendant wants to bring in an insurer or indemnitor, ask in order: Is the proposed party still a nonparty? Is the proposed liability derivative of the plaintiff’s claim? Is the filing within 14 days after the original answer? If not, has leave been obtained? Only then consider the additional claims and jurisdiction.

Intervention at the Courthouse Door: Right, Permission, and the Worked Item

Intervention differs from party joinder because the nonparty seeks entry into an existing action rather than being added by an existing litigant. Under Rule 24(a), intervention of right requires a timely motion and one of two routes:

A federal statute gives the applicant an unconditional right to intervene; or
The applicant claims an interest relating to the property or transaction that is the subject of the action, the disposition may impair or impede the applicant’s ability to protect that interest, and existing parties do not adequately represent it.

The second route has four practical elements: timeliness, a qualifying interest, possible impairment of that interest, and inadequate representation. An economic or legally protected interest must be connected to the property or transaction in the lawsuit. A shared issue alone is not enough. Nor is possible practical harm enough if the existing parties adequately represent the applicant’s position. Intervention of right is mandatory only when every required condition is met; it is not automatic merely because the applicant prefers to participate.

Under Rule 24(b), permissive intervention is available, on a timely motion, when either a federal statute gives a conditional right to intervene or the applicant has a claim or defense sharing a common question of law or fact with the main action. The court has discretion to allow or deny it and must consider whether intervention would cause undue delay or prejudice. Commonality is the key separator: it can support permissive intervention, but it does not replace the interest, impairment, and inadequate-representation requirements for intervention of right.

Neither Rule 24(a) nor Rule 24(b) itself supplies subject-matter jurisdiction. The court must have an independent jurisdictional basis or valid supplemental jurisdiction under § 1367, including the diversity-based limits in § 1367(b).

Question	Intervention of right under Rule 24(a)	Permissive intervention under Rule 24(b)
Timing	Timely motion required	Timely motion required
Applicant’s showing	Unconditional statutory right, or interest, possible impairment, and inadequate representation	Conditional statutory right, or claim or defense sharing common law or fact question
Court’s role	Must allow if requirements are satisfied	May allow or deny
Main limiting concern	Existing parties’ inadequate representation	Undue delay or prejudice
Jurisdiction	Rule 24 does not supply it	Rule 24 does not supply it

The following sequence is confined to whether intervention of right has been established:

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A defendant served an answer 10 days ago in a negligence action arising from a collision. The defendant discovers that an indemnity agreement may require a nonparty insurer to reimburse the defendant for any amount the defendant owes the plaintiff. The defendant wants to bring the insurer into the action.

The defendant files a third-party complaint against the insurer 10 days after serving the original answer.

The insurer argues that it cannot be joined because the indemnity agreement was separate from the collision and the insurer was not named in the plaintiff’s complaint.

The defendant’s proposed claim seeks reimbursement for any liability imposed on the defendant.

Practice

May the defendant serve the third-party complaint without first obtaining court leave?

Recurring errors include:

Treating a defendant’s claim against a codefendant as a counterclaim when the concrete fact is that the target is a co-party, making it a crossclaim under Rule 13(g).
Calling every related claim compulsory when the claim does not arise from the same transaction or occurrence or requires an unavailable additional party.
Using Rule 14 to add a person alleged to be directly liable to the plaintiff rather than a person who may owe the defending party contribution or indemnity.
Assuming proper Rule 20 joinder guarantees one trial when the court may sever under Rule 21 or order separate trials under Rule 42(b).
Treating a shared legal issue as intervention of right when the applicant lacks a related interest, possible impairment, or inadequate representation.

Three Pressure Tests: Rules That Decide the Device

Practice

A borrower sues a lender for breaching a loan agreement. The lender has an unrelated claim that the borrower failed to repay a separate personal loan. The lender wants to assert the personal-loan claim in the pending action. Which is most accurate?

A plaintiff properly joins two defendants and asserts separate claims arising from the same series of transactions. One defendant moves to separate the claims because trying them together would cause substantial jury confusion. What may the court do?

A property owner timely moves to intervene in a suit challenging a construction permit. The owner claims that the judgment could impair the owner’s property interest, but the existing parties already present and protect precisely the owner’s position. The owner also shares a factual issue with the main action. What is the best result?

High-Yield Points - ⚡ Biggest Takeaways

Use Rule 18 for more claims against an existing opponent and Rule 20 for adding parties. A compulsory counterclaim shares the opposing claim’s transaction or occurrence; a crossclaim targets a co-party. Rule 14 requires derivative liability, while Rule 21 and Rule 42(b) let the court separate even proper joinder. Rule 24(a) requires interest, impairment, and inadequate representation; Rule 24(b) turns on commonality and discretion.

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Practice Questions: Joinder of claims, parties and intervention

1. A consumer filed a products-liability action in federal court based solely on diversity jurisdiction. The consumer demanded a jury trial. State substantive law supplies the elements of the claim and recognizes assumption of risk as a defense. A state statute directs judges to decide disputed facts concerning assumption of risk before trial and bars submission of that defense to a jury. Federal practice, implementing the federal jury-trial right, assigns genuinely disputed factual issues on legal claims to the jury. The manufacturer asks the federal judge to follow the state statute and decide the disputed defense facts. The consumer argues that the federal allocation applies. Which of the following best states how the court should resolve the issue?

A. Apply the state rule because state law governs every issue closely connected to the elements of a state-law claim.
B. Apply the state rule because federal courts must use state procedures whenever they could affect litigation outcomes.
C. Apply the federal practice only if the manufacturer proves that the state rule was designed to discriminate against federal litigation.
D. Apply the federal practice because federal jury-trial law governs the allocation of functions between judge and jury in federal court.

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Answer: D. Apply the federal practice because federal jury-trial law governs the allocation of functions between judge and jury in federal court.

Apply the federal practice because federal jury-trial law governs the allocation of functions between judge and jury in federal court. - State law defines assumption of risk as a defense to the consumer’s claim. - Federal jury-trial law governs who decides genuinely disputed facts on a legal claim in federal court, so the jury decides those defense facts. Apply the state rule because state law governs every issue closely connected to the elements of a state-law claim. - The state-law source of the defense does not make its judge–jury allocation rule substantive. - The court applies state law to the defense’s elements, but federal law to the allocation of factfinding. Apply the state rule because federal courts must use state procedures whenever they could affect litigation outcomes. - Having the judge rather than the jury decide disputed defense facts could affect the outcome, but outcome effect alone does not control. - The federal interest in preserving the jury’s factfinding role on legal claims supports applying federal practice. Apply the federal practice only if the manufacturer proves that the state rule was designed to discriminate against federal litigation. - Federal jury-trial practice does not depend on proof that the state statute was intended to discriminate against federal litigation. - The disputed question is who decides the defense facts, not why the state adopted its rule.

3. Using only the supplied file and legal resources, prepare a persuasive motion and supporting memorandum requesting the most appropriate route to a final appealable judgment on Rowan's resolved claim. Address finality, separability, reasons for and against certification, preservation, and any separate relief needed to protect Summit during appellate proceedings.

4. Using only the supplied file and legal resources, prepare a persuasive opposition outline addressing Titan Manufacturing's renewed motion for judgment as a matter of law and alternative motion for a new trial. Analyze preservation, the distinct standards for each motion, the evidentiary record, the proper scope of any new trial, and the steps counsel should take to protect Bell's position on appeal.

5. Using only the supplied file and legal resources, prepare an objective memorandum assessing the preclusive effect of the prior judgment on Metro Workspace's new action and recommending Harbor's most appropriate procedural response.

8. A pedestrian sued a delivery company in federal court for negligence after one of the company's vans struck her in a crosswalk. After discovery, the company moved for summary judgment and submitted an affidavit from the driver stating that the traffic signal was green for the van. The pedestrian submitted deposition testimony from an eyewitness who stated that the signal was red and that the driver was looking at a phone. Both witnesses had a clear view of the intersection, and the governing negligence law is undisputed. The company argues that its driver gave a more detailed account and has a stronger memory than the eyewitness. Is the court likely to grant the motion?

A. Yes, because a court may credit the more detailed testimony when both witnesses claim firsthand knowledge.
B. No, because the conflicting firsthand accounts create a genuine dispute that a factfinder must resolve.
C. Yes, because testimony from a party's employee is entitled to greater weight than testimony from an uninvolved observer.
D. No, because summary judgment is unavailable whenever a negligence claim turns partly on witness testimony.

Show answer

Answer: B. No, because the conflicting firsthand accounts create a genuine dispute that a factfinder must resolve.

No, because the conflicting firsthand accounts create a genuine dispute that a factfinder must resolve. - The driver said the signal was green, while the eyewitness said it was red and the driver was looking at a phone, creating a genuine dispute of material fact about negligence. - Because both witnesses had a clear view, the court cannot decide whose account is more credible on summary judgment. Yes, because a court may credit the more detailed testimony when both witnesses claim firsthand knowledge. - The driver’s greater detail and asserted stronger memory do not let the court weigh competing testimony on summary judgment. - Those arguments belong to the factfinder, which must resolve the conflicting accounts. Yes, because testimony from a party's employee is entitled to greater weight than testimony from an uninvolved observer. - The driver’s status as a company employee gives his affidavit no special weight over the eyewitness’s deposition testimony. - Both accounts concern what happened at the intersection, so the court cannot prefer one merely because of the witness’s relationship to the company. No, because summary judgment is unavailable whenever a negligence claim turns partly on witness testimony. - Negligence claims can be resolved by summary judgment when the evidence presents no genuine dispute of material fact. - Denial is warranted here because the witnesses conflict about the signal and the driver’s conduct, not because the claim involves witness testimony.

9. A customer sued a grocery store in federal court after slipping and falling on a wet floor near the produce section. The customer testified at her deposition that no warning sign was posted and that a nearby employee was texting on his phone instead of watching the area. The employee submitted a declaration stating that a warning sign was in place, that the customer was jogging through the aisle, and that he was not using his phone. The store's security video shows the fall but does not clearly show whether a sign was present or what the employee was doing with his hands. After discovery closed, the store moved for summary judgment and argued that the employee's detailed declaration was more reliable than the customer's testimony. Neither side objected to the admissibility of the cited evidence. Is the court likely to grant the motion?

A. Grant summary judgment because the employee's sworn testimony is more credible than the customer's deposition testimony.
B. Grant summary judgment because the customer bears the burden of proving negligence at trial.
C. Deny summary judgment only if the customer submits evidence conclusively proving that no warning sign was posted.
D. Deny summary judgment because the conflicting testimony creates a genuine dispute of material fact for the jury.

Show answer

Answer: D. Deny summary judgment because the conflicting testimony creates a genuine dispute of material fact for the jury.

Deny summary judgment because the conflicting testimony creates a genuine dispute of material fact for the jury. - The customer and employee give conflicting accounts of the warning sign and the employee’s conduct, facts relevant to whether the store acted negligently. - Because the video does not resolve those conflicts, the court must view the evidence in the customer’s favor rather than decide whose account is more credible. Grant summary judgment because the employee's sworn testimony is more credible than the customer's deposition testimony. - The employee’s declaration and the customer’s deposition are both evidence the court may consider; a declaration is not inherently more credible. - Deciding which witness to believe would improperly resolve a credibility dispute at summary judgment. Grant summary judgment because the customer bears the burden of proving negligence at trial. - The customer does bear the trial burden, but her deposition testimony supplies evidence supporting her account. - That burden does not allow the court to disregard her testimony in favor of the employee’s conflicting declaration. Deny summary judgment only if the customer submits evidence conclusively proving that no warning sign was posted. - The customer need not conclusively prove the absence of a sign to defeat summary judgment. - Her testimony that no sign was posted conflicts with the employee’s declaration, and the video does not settle the issue.

Flashcards: Joinder of claims, parties and intervention

1. What are the four practical elements required for intervention of right under Rule 24(a)?

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Timeliness, a qualifying interest, possible impairment of that interest, and inadequate representation by existing parties.

2. What are the two requirements for permissive joinder of parties under Rule 20?

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The claims must arise out of the same transaction, occurrence, or series of transactions or occurrences; and the claims must present at least one common question of law or fact.

3. What is the required basis for factual contentions under Rule 11(b)?

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Factual contentions must have evidentiary support, or, if specifically identified, be likely to have evidentiary support after a reasonable opportunity for further investigation or discovery.

4. What is the heightened pleading standard for allegations of fraud or mistake under federal rules?

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Under Rule 9(b), a party alleging fraud or mistake must state with particularity the circumstances constituting fraud or mistake (the who, what, when, where, and how). However, malice, intent, knowledge, and other conditions of a person’s mind may be alleged generally.

5. Under what circumstances may a party amend its pleading once as a matter of course?

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A party may amend its pleading once as a matter of course within 21 days after serving it, or if a responsive pleading is required, within 21 days after service of a responsive pleading or a motion under Rule 12(b), (e), or (f), whichever is earlier. (Rule 15(a)(1))

6. What is the primary purpose of a Rule 11 sanction, and what is its key limitation?

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The primary purpose of a Rule 11 sanction is to deter repetition of the conduct or comparable conduct. It is limited to what suffices for deterrence and is not automatically compensatory or punitive.

7. What is the 'safe harbor' provision under Rule 11 for a motion for sanctions?

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A party moving for Rule 11 sanctions must serve the motion on the opposing party but not file it with the court for 21 days. This allows the offending party to withdraw or correct the challenged paper, avoiding sanctions.

8. What specific conditions must be met for a federal court to issue a temporary restraining order (TRO) without notice to the adverse party?

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A court may issue an ex parte TRO only if: 1) specific facts in an affidavit or verified complaint clearly show immediate and irreparable injury before the adverse party can be heard; AND 2) the movant’s attorney certifies in writing efforts made to give notice and reasons why it should not be required.