⚡ 10-Second Rule
Courts like solving one whole mess in one case, with everyone who truly matters in the room.
🧒 ELI-10 Scene
At game night, Theo knocks over a juice pitcher. It soaks the game board, ruins Ava's controller, and stains Grandpa Lou's antique rug. Mom refuses to hold three separate family meetings. One spill, one meeting: Ava and cousin Ben both bring their complaints about the same splash. And because it's Grandpa Lou's rug, Mom won't decide the rug question without him at the table. One more twist: Theo says Ava actually bumped his elbow. He has to raise that now, at this meeting — not save it for revenge next week.
⚖️ Actual Rule
Rule 18(a) lets a party assert "as many claims as it has against an opposing party," related or not. Rule 20(a) permits plaintiffs to join together, or to sue multiple defendants together, when the claims arise out of the same transaction, occurrence, or series of transactions or occurrences, and any question of law or fact is common to all. Rule 19(a) makes a person a required party if, in that person's absence, the court cannot accord complete relief among existing parties, or the person claims an interest that the case may as a practical matter impair, or whose absence leaves an existing party at risk of double or inconsistent obligations. If joining the required party is not feasible — typically because joinder would destroy diversity or personal jurisdiction is lacking — Rule 19(b) asks whether the action should proceed or be dismissed, weighing: the extent of prejudice to the absentee or existing parties; whether protective provisions or shaping of relief can lessen that prejudice; whether a judgment rendered without the absentee would be adequate; and whether the plaintiff would have an adequate remedy if the case were dismissed.
Rule 13(a) makes a counterclaim compulsory if it "arises out of the transaction or occurrence that is the subject matter of the opposing party's claim" and requires no party beyond the court's jurisdiction; a compulsory counterclaim not asserted is barred in later litigation. Rule 13(b) permits any other counterclaim. Rule 13(g) allows a crossclaim against a co-party arising from the same transaction or occurrence as the original action or a counterclaim — crossclaims are always optional, never compulsory.
ELI-10 translation: related complaints ride together, must-have people get seats, and same-spill counterattacks are use-it-or-lose-it.
🔍 Ask These Questions
- Is this a party stacking its own claims against an opponent under Rule 18? (Once you're already arguing, you may unload every complaint you have.)
- Are multiple plaintiffs or defendants joined under Rule 20 — same transaction plus a common question? (Everyone splashed by the same spill can share one meeting.)
- Is an absent person required under Rule 19(a) — complete relief, impaired interest, or double-obligation risk? (Can the rug be decided fairly without Grandpa Lou?)
- If the required person can't be joined, do the Rule 19(b) factors favor proceeding or dismissing? (If the must-have guest can't come, hold the meeting carefully or cancel it.)
- Is the defendant's claim back a compulsory counterclaim — same transaction or occurrence? (A counterattack about the same spill must be raised now or never.)
- Is a claim against a co-party a proper crossclaim under Rule 13(g)? (Teammates may blame each other about the same mess, but nobody has to.)
⚠️ Bar Trap
Exam language: Examiners have a defendant litigate to judgment without asserting a same-transaction claim against the plaintiff, then file that claim as a fresh suit. Rule 13(a) bars it. The mirror trap runs the other way: a crossclaim against a co-party, or a counterclaim arising from an unrelated transaction, is never compulsory, so failing to raise it forfeits nothing.
ELI-10: If your counterattack comes from the same accident, use it now or lose it forever. Attacks on teammates, or about different accidents, can always wait.
🧪 Question
A florist's delivery van and a baker's delivery van collided at an intersection, injuring both drivers and damaging both vehicles. The baker sued the florist in federal district court, properly invoking diversity jurisdiction, seeking $80,000 for vehicle damage. The florist answered, denying negligence, and the case proceeded to a judgment for the baker. Eight months later, the florist sued the baker in a different federal district court, seeking $95,000 for her own injuries sustained in the same collision. The baker moves to dismiss the florist's action.
How should the court rule on the motion?
(A) Grant the motion, because the florist's claim was a compulsory counterclaim in the first action and is now barred. (B) Deny the motion, because a plaintiff is entitled to choose the forum for her own affirmative claim. (C) Deny the motion, because counterclaims are permissive and may be brought in a separate action. (D) Grant the motion, because a final judgment always precludes any later suit between the same two parties.
Answer: (A). The florist's injury claim arises out of the same collision that was the subject matter of the baker's claim, no absent party was needed, so Rule 13(a) made it compulsory; having failed to plead it in the first action, the florist is barred from asserting it now.
💡 Why the Wrong Answers Are Wrong
- (B) invokes forum choice, which never overrides Rule 13(a); a compulsory counterclaim must be brought in the pending action, not a preferred court later.
- (C) describes Rule 13(b) permissive counterclaims, which arise from different transactions; a same-collision claim falls squarely under 13(a).
- (D) overstates preclusion; final judgments bar the same claim and issues actually decided, not every conceivable suit between the parties — the bar here comes specifically from Rule 13(a).
- ELI-10: The misconception is thinking you can always save your counterattack for later. Same accident means same lawsuit, whether you like the courtroom or not.
