Breaking Down Diversity Jurisdiction and Claim Aggregation

Emily Carter

Hey everyone, welcome back to the Civil Procedure Midterm Study Guide. I’m Emily, and David’s here with me as always. Today, we’re dissecting diversity jurisdiction—you’ve probably seen this all over 28 U.S.C. § 1332, right? But it’s more than just a couple of buzzwords for the midterm.

David Reynolds

Indeed, Emily. If you remember from last time, when we talked about those 'three rings' of jurisdiction, diversity fits squarely into the subject-matter category for federal courts. So, the statute requires two things: first, an amount in controversy greater than $75,000, and second—this is crucial—'complete diversity' between all plaintiffs and all defendants, going all the way back to Strawbridge v. Curtiss. No overlap allowed, which can trip people up.

Emily Carter

Yeah, and people get tripped up even just over what “citizenship” means. So, for individuals, it's not just where you live—domicile is all about physical presence and the intent to remain. The Gordon v. Steele case really hammered that home. Like, I had my first mock trial as a 1L and got grilled about the difference between residency and domicile! Classic law school moment. For example, say there’s a student from Texas going to school in New York—if she really still plans to go back to Texas after graduation, Texas is still her domicile, even if her current address is New York. Happens all the time.

David Reynolds

Yes, that's absolutely right, Emily. Now for corporations, it gets a touch more technical—their citizenship is both their state of incorporation and their principal place of business. And the Supreme Court clarified in Hertz that the principal place of business is—what do they call it? The 'nerve center,' precisely. Usually wherever the execs make the big decisions, like headquarters. But for LLCs or limited partnerships, every single member or partner’s citizenship counts, so it’s almost always a bit… unwieldy, if I’m honest.

Emily Carter

Oh, totally unwieldy, David. And just to tie it back to why this matters, if you mess up the citizenship analysis, your whole federal case could get tossed for lack of subject-matter jurisdiction. Which would be, uh, embarrassing—both on an exam and in real life.

Emily Carter

Let’s dig a bit deeper into those cases we mentioned—because you will absolutely see these pop up in hypos or on your midterm. Gordon v. Steele: long story short, a woman moves away for school but intends to go back home eventually. Court says domicile stays with you until you physically move somewhere different and actually plan to stay for good. That intent piece is pretty subjective, but if your driver's license, voter registration, or even stuff like where your dentist is—if it all points to one place, that's solid evidence of intent.

David Reynolds

Mas v. Perry is quite similar—two married students from different countries study in Louisiana. They have no intention of making Louisiana their permanent home, so their original citizenships persist. Domicile isn’t lost until a new one’s acquired, and all the little details count. The principle has real reach, actually—I once knew a British student studying at Yale. Visas, leases, travel plans—her circumstance meant she never lost her U.K. domicile because there was no intent to remain in the U.S.

Emily Carter

I remember Hertz v. Friend too—so many people mess up the nerve center thing on practice exams. But it makes sense for big corporations that do business everywhere. The question is: Where are the top execs pulling the strings every day? That’s the nerve center, not where the most employees are, or where the factories are, even if those numbers are huge.

David Reynolds

Quite. And all of these cases inform how lawyers analyze jurisdiction before they even file—because federal judges absolutely spot these issues straight away. It’s also why venue shopping is such a thing, but, er, that’s a tangent for another episode.

David Reynolds

Moving right along, let’s talk claim aggregation—because this always comes up right after the basics on diversity. Alright, so if you’ve got a single plaintiff with multiple claims against one defendant, you can add up the dollar amounts—doesn’t matter if the claims have nothing to do with each other. Long as the total crosses that $75,000 threshold, you’re set for the amount in controversy.

Emily Carter

But—and this is a big “but”—if you’ve got multiple plaintiffs, they can’t just combine their claims to create jurisdiction unless at least one plaintiff independently meets the $75,000 requirement. This was really hammered out in Exxon v. Allapattah. The Supreme Court said if one person qualifies, others with related claims under the same case or controversy can come along under supplemental jurisdiction—even if their claims are less than $75K individually. But complete diversity still has to exist for everyone. Super important.

David Reynolds

Yes, and to clarify, the logic now is, as long as one person’s got a proper case in federal court based on diversity, the supplemental jurisdiction statute—section 1367—lets the court hear those additional related state law claims. Congress really broadened federal jurisdiction unless there’s a specific statutory restriction.

Emily Carter

Let me throw out a hypo to bring it home—a classic textbook scenario. Four friends injured in separate car accidents, all involving the same trucking company. Only one of them, say, Jess, has medical bills over $75,000—the rest are lower. Jess can sue in federal court. Her friends? They can tag along because their claims are tied to the same defendant and facts—that’s the CNOF, or “common nucleus of operative fact,” test in action—but only because Jess meets the amount-in-controversy threshold herself. If none of them cleared $75K, they’d all be stuck in state court, no matter how compelling the story.

David Reynolds

That’s the essence of aggregation. Simple in theory, a headache in practice. But I think that’s a solid stopping point for this breakdown. Emily, any last words of wisdom for our listeners?

Emily Carter

Just that, honestly, these distinctions are everywhere on exams and in real cases. Don’t panic if you mix up domicile or aggregation rules the first time—it takes practice. We’ll keep drilling them. Alright, that’s all for today. David, thanks for nerding out on this with me!

David Reynolds

Always a pleasure, Emily. And thank you, everyone, for tuning in. We’ll catch you next episode when we tackle supplemental jurisdiction. Until next time!