In legal terms, MDL stands for multidistrict litigation, a federal court procedure that temporarily transfers lawsuits sharing common facts from courts around the country into a single courtroom for pretrial work. It is not a merger of cases and not a single lawsuit. Each plaintiff keeps their own complaint, their own lawyer, and their own claim for damages; only the shared pretrial work happens in one place, before one judge. As of December 2025, 157 active MDL dockets were pending in the federal courts, holding more than 198,000 individual lawsuits.1United States Judicial Panel on Multidistrict Litigation. Pending MDL Dockets By Actions Pending – December 2, 2025
The problem MDL solves is duplication. When thousands of people sue the same defendant over the same product, each case would otherwise generate its own discovery, its own motions, and its own rulings. Different judges could reach opposite conclusions on identical questions. MDL centralizes the shared work while preserving each plaintiff’s individual case.
Who Decides to Create an MDL
A specialized body called the Judicial Panel on Multidistrict Litigation (JPML) makes the call. Congress created it in 1968 through 28 U.S.C. § 1407. Seven sitting federal judges sit on the panel, appointed by the Chief Justice of the United States, and no two can come from the same federal circuit.2United States Judicial Panel on Multidistrict Litigation. About the Panel Four of the seven must agree before the panel can act.3Office of the Law Revision Counsel. 28 U.S. Code 1407 – Multidistrict Litigation
The panel uses a two-part test: whether transfer would be convenient for the parties and witnesses, and whether it would promote the just and efficient handling of the lawsuits.3Office of the Law Revision Counsel. 28 U.S. Code 1407 – Multidistrict Litigation Any party in one of the related cases can ask for consolidation, and the panel can also start the process on its own.4GovInfo. 28 U.S. Code 1407 – Multidistrict Litigation> When the JPML grants transfer, it picks a single federal district court (the “transferee court”) and assigns one judge to run all pretrial proceedings.
How Individual Cases Get Pulled In
The initial transfer order moves every case the panel identified. MDLs rarely stay static after that, though. New lawsuits keep getting filed around the country involving the same facts, and they can be added through what the JPML’s rules call conditional transfer orders. Parties who object have a short window to say so; if nobody objects, the transfer goes through automatically. Cases added this way are commonly known as “tag-along actions.”5United States Judicial Panel on Multidistrict Litigation. Rules of Procedure
A case filed directly in the district where the MDL is already pending doesn’t need a panel transfer at all. The local court simply assigns it to the MDL judge under that district’s local rules.
What Happens Inside an MDL
Once cases arrive at the transferee court, the assigned judge controls everything that happens before trial.
Leadership Counsel and the Common Benefit Fund
One of the judge’s first tasks is appointing a leadership structure for the plaintiffs. The judge selects lead counsel and a plaintiffs’ steering committee (PSC). Lead counsel sets overall strategy, coordinates discovery, files motions, and negotiates settlement. The PSC handles day-to-day work: reviewing documents, preparing depositions, and managing expert science.
That leadership work benefits every plaintiff in the MDL, not just the leadership lawyers’ own clients. To compensate them, MDL courts typically create a “common benefit fund,” assessed as a percentage of eventual settlements or verdicts. The cost assessment commonly falls in the 4–6 percent range and comes out of settlement proceeds. The fee component is paid from each plaintiff’s own attorney’s contingency fee, not added on top, so plaintiffs are not charged an extra attorney fee for the leadership structure.
Consolidated Discovery and Pretrial Motions
Discovery that would have taken place separately in dozens of courtrooms happens once. Key witness depositions, production of corporate documents, and expert proceedings all run on an MDL-wide basis. The judge also rules on pretrial motions that affect the entire litigation. A ruling that a product was not defective, for example, can resolve thousands of cases in a single order.
Bellwether Trials
Many MDLs use “bellwether” trials. The court picks a small number of representative cases and tries them to verdict so both sides can see how juries actually respond to the evidence. The court identifies the key characteristics of the full case pool, builds a subset reflecting those characteristics, advances that subset through discovery, and picks specific cases from that group for trial.
Both sides push to shape the pool. Plaintiffs want the strongest cases tried first; defendants want the weakest. A transferee judge who is doing the job well insists the bellwethers be genuinely representative. The verdicts don’t bind other plaintiffs, but they heavily influence settlement talks. A run of plaintiff wins pushes defendants toward a global deal; defense verdicts have the opposite effect.
MDL Is Not a Class Action
The confusion is common, and the differences are substantial.
- In a class action, one or a few named plaintiffs represent an entire group, and class members are bound by the outcome unless they opt out. In an MDL, each plaintiff filed their own lawsuit. There is nothing to opt in or out of because the cases were never merged.
- Class members generally have no individual attorney handling their claim. MDL plaintiffs hire their own lawyer, who files an individual complaint and advocates for that client specifically, even though leadership counsel runs the shared pretrial work.
- Class settlements usually pay a uniform amount or apply a rigid formula. MDL settlements can account for differences in injury severity, duration of exposure, or other case-specific facts, because each case was always separate.
The two do occasionally overlap. A transferee judge can certify a class within an MDL for a specific issue, like whether marketing was misleading, while keeping individual damage claims separate.
How MDLs End
Most MDL cases never reach a jury. Consolidated discovery, pretrial rulings, and bellwether outcomes usually give both sides enough information to negotiate. Large MDLs frequently end in a global settlement covering all or most of the cases, often through a claims program with compensation tiers keyed to injury type and severity.
Cases that don’t settle go back home. The statute requires the JPML to remand unresolved cases to the courts where they were originally filed. In Lexecon Inc. v. Milberg Weiss, the Supreme Court held that a transferee judge has no authority to keep a case for trial: § 1407’s mandatory language means transferred cases “shall be remanded” once pretrial work is done.6Legal Information Institute. Lexecon Inc. v. Milberg Weiss Bershad Hynes and Lerach That rule creates real pressure to settle. Once cases scatter back to their home districts, the efficiency of centralization disappears and both sides face the prospect of hundreds of individual trials.
What Kinds of Cases Become MDLs
MDLs overwhelmingly arise from product liability and mass tort situations where one product or substance injures a large number of people in similar ways. Pharmaceutical and medical device cases dominate. Some of the largest MDLs in history have involved defective combat earplugs, talcum powder contamination, hernia mesh implants, firefighting foam chemicals, and hip replacement devices, each holding thousands to hundreds of thousands of individual claims.1United States Judicial Panel on Multidistrict Litigation. Pending MDL Dockets By Actions Pending – December 2, 2025
Beyond product liability, MDLs also handle data breach litigation, environmental contamination, financial fraud, and antitrust disputes. The common thread is the same in every one: a large number of people harmed by the same conduct, filing separate federal lawsuits that share overlapping questions of fact.