Claim Splitting

Claim splitting refers to a patent plaintiff dividing a single legal claim or cause of action across multiple lawsuits when those claims should properly be brought together in a single proceeding: GENERAL DEFINITION: under general res judicata principles, a plaintiff must bring all related claims in a single action; splitting a single cause of action into multiple suits is prohibited — the second suit is barred by claim preclusion even if the plaintiff could have won on the unasserted ground; PATENT-SPECIFIC CONTEXT: in patent enforcement, claim splitting issues arise when: (1) a patent owner has multiple patents and sues for infringement of only some patents, then files a second suit on the others; (2) a patent owner asserts only some claims from a patent in the first suit, then asserts the remaining claims in a second suit; (3) a patent owner sues for past infringement, then files a second suit for ongoing infringement of the same product; FEDERAL CIRCUIT APPROACH: the Federal Circuit has addressed whether claim preclusion bars subsequent suits on patent claims not asserted in a prior action; the key question is whether the later suit arises from the same 'claim' or cause of action as the first; TRANSACTIONAL TEST: courts apply a transactional analysis — if the second suit arises from the same transaction or occurrence as the first, it is the same claim; asserted patent claims that arise from the same accused product during the same period may be a single cause of action; DIFFERENT PATENTS = DIFFERENT CLAIMS: patent owners who have multiple patents covering the same product may be able to file separate suits on each patent — if courts treat each patent as a separate cause of action — but this is not uniformly accepted.

Claim preclusion bars a second suit when the elements are met and the plaintiff improperly split claims that should have been in the first suit: REQUIRED ELEMENTS FOR PRECLUSION: (1) prior final judgment on the merits; (2) same parties (or privity); (3) same claim/cause of action; IF ALL THREE ARE MET AND THE PLAINTIFF SPLIT CLAIMS: the second suit is barred — even if the plaintiff could have won; SAME CLAIM IN PATENT CONTEXT: the Federal Circuit has ruled that a claim for infringement of DIFFERENT PATENT CLAIMS from the same patent — on the same accused product — may be treated as the same cause of action if they arise from the same transaction; a patent owner who asserts Claims 1-5 in a first suit and wins/loses may be barred from asserting Claims 6-10 of the same patent against the same product in a second suit; DIFFERENT PATENTS ON SAME PRODUCT: whether infringement of Patent A and Patent B, both covering the same accused product, constitutes the same cause of action is less clear; some courts treat each patent as a separate cause of action; others apply a transactional test; DIFFERENT TIME PERIODS: infringement occurring after the first judgment is generally a new cause of action (future infringement); but if the defendant's ongoing conduct is essentially unchanged from the first suit period, courts are divided; COMPLICATING FACTOR — PATENT ISSUANCE: if a patent issues during or after the first suit, the patent owner could not have asserted it in the first suit; a suit on a newly-issued patent is generally not claim-split barred because the claim arose after the first judgment.

The Federal Rules of Civil Procedure contain a compulsory counterclaim rule that interacts with patent claim splitting: RULE 13(a) COMPULSORY COUNTERCLAIMS: a party defending against a claim must assert any counterclaim that 'arises out of the transaction or occurrence that is the subject of the opposing party's claim' and does not require adding parties over whom the court lacks jurisdiction; failure to assert a compulsory counterclaim forfeits the claim — it CANNOT be raised in a separate lawsuit; PATENT COUNTERCLAIMS — INVALIDITY: in a patent infringement suit, an accused infringer who does not assert invalidity as a counterclaim in the first suit may be precluded from asserting invalidity in a second suit (via issue preclusion if the first suit ended with a validity finding, or via compulsory counterclaim rules); PATENT COUNTERCLAIMS — DIFFERENT PATENTS: if Party A sues Party B for infringing Patent 1, and Party B has its own Patent 2 that Party A infringes, Patent 2 infringement claims may be compulsory counterclaims if they arise from the same transaction (the same technology area and product); if not asserted, they may be barred; DECLARATORY JUDGMENT COUNTERCLAIMS: an accused infringer who files a DJ action for non-infringement or invalidity has standing; if a DJ action is filed, the patent owner's infringement claims are (likely) compulsory counterclaims and must be filed in response or risk waiver; PATENT-SPECIFIC EXCEPTION — 35 U.S.C. § 299: for patent suits against multiple defendants, the AIA restricted joinder; claim splitting and counterclaim rules apply on a per-defendant basis rather than across all defendants in one mega-suit.

Experienced patent litigators structure enforcement campaigns to preserve flexibility while minimizing claim splitting risk: SAME ACCUSED PRODUCT — ASSERT ALL RELEVANT CLAIMS AND PATENTS AT ONCE: the safest approach is to assert all patents and all relevant claims in a single suit against the same accused product; waiting to assert additional patents in later rounds on the same product is risky; FILE CONTINUATION PATENTS STRATEGICALLY: because newly-issued patents generally cannot be claim-split barred (they did not exist at time of first suit), patent owners who have pending continuations may time issuance of new claims to preserve future suit rights; DIFFERENT ACCUSED PRODUCTS = DIFFERENT CAUSES OF ACTION: suits targeting genuinely different products from the same defendant are generally separate causes of action — no claim splitting concern; STRUCTURE SETTLEMENTS WITH CARE: settlement agreements that release 'all claims known or unknown' in exchange for a lump sum may bar future suits on related patents; careful drafting of release scope preserves future enforcement rights; CONSOLIDATION VS. SEPARATE SUITS: patent owners may prefer to consolidate all patents against all products in one case for efficiency; or may strategically sequence: first suit to establish validity and claim construction; second suit on different products using the established claim construction; BUT BEWARE: the Kessler doctrine and preclusion rules can bite if the later suit attempts to relitigate what was decided in the first; MONITORING DEFENDANT'S PRODUCTS: patent owners should monitor product changes; a 'more than colorably different' new product is a new cause of action (Acumed v. Stryker); the same accused product is not.

Claim splitting, the Kessler doctrine, and patent exhaustion all limit a patent owner's ability to make multiple enforcement bites at the same commercial transaction: CLAIM SPLITTING (RES JUDICATA LIMITATION): prevents a patent owner from splitting a single cause of action across multiple suits; protects defendants from litigating piecemeal; applies to parties to the litigation (or those in privity); KESSLER DOCTRINE (PROTECTING MANUFACTURERS AND CUSTOMERS): Kessler v. Eldred (S.Ct. 1907): a manufacturer who obtains a non-infringement judgment acquires a 'limited license' protecting itself and its customers from subsequent suits by the same patentee on the same products; the patent owner cannot do an end-run around the non-infringement judgment by suing customers who buy the adjudicated non-infringing product; PATENT EXHAUSTION (FIRST SALE DOCTRINE): Impression Products v. Lexmark International (S.Ct. 2017): once a patent owner (or authorized licensee) makes an authorized sale of a patented article, the patent owner's rights in that specific item are exhausted; the patent owner cannot sue downstream purchasers for patent infringement based on using or reselling the authorized item; exhaustion is transactional — it applies to each authorized sale; HOW THEY INTERACT: (1) Claim splitting prevents patentee from asserting unasserted claims from a prior suit; (2) Kessler prevents patentee from re-attacking adjudicated products via customer suits; (3) Exhaustion prevents patentee from asserting infringement against downstream purchasers of authorized articles; together, these three doctrines limit repetitive patent enforcement and protect the commercial predictability of once-authorized transactions.