Copyright Infringement Litigation and the Proof Required

By Hank FasthoffJuly 7, 2026

Copyright protects original expression once an author fixes it in a tangible medium. A lawsuit requires more. A copyright owner must prove ownership of a valid copyright and copying of protectable expression, then connect the requested remedy to admissible evidence and the Copyright Act.

Federal district courts have exclusive jurisdiction over claims arising under the Copyright Act under 28 U.S.C. Section 1338. Copyright disputes also produce contract, ownership, accounting, and state law claims, but federal law governs the infringement claim.

Ownership, Fixation, and Registration

An original work receives copyright protection when it's fixed in a tangible medium of expression. Originality requires independent creation and at least a minimal degree of creativity under Feist Publications, Inc. v. Rural Telephone Service Co., 499 U.S. 340 (1991). Fixation occurs when the author records, writes, saves, photographs, films, or otherwise captures the expression in a form that permits perception or reproduction for more than a transitory period.

Authorship and current ownership can involve different people. An author can assign the copyright, an employer can own a work for hire, coauthors can own undivided interests, and an estate can acquire rights after an author's death. Before filing, you should confirm the chain of title, identify each written transfer, and compare the asserted rights against any licenses, assignments, corporate records, and estate documents. Our article on copyright assignments and transfers addresses those ownership documents in detail.

A registration certificate issued before or within five years after first publication constitutes prima facie evidence of copyright validity and the facts stated in the certificate under Section 410(c). That presumption affects who must produce evidence on validity, but defendants can dispute authorship, protectability, ownership, or the scope of any transfer.

Registration controls when a plaintiff can sue over a United States work. Section 411(a) requires registration or refusal before filing an infringement action, subject to the exceptions written into the statute. In Fourth Estate Public Benefit Corp. v. Wall-Street.com, LLC, 586 U.S. 296 (2019), the Supreme Court held that registration occurs when the Copyright Office acts on the application, rather than when the applicant submits it.

An error in an application doesn't automatically invalidate a registration. Section 411(b) requires a court to ask the Register of Copyrights whether known inaccurate information would have caused a refusal, and Unicolors, Inc. v. H&M Hennes & Mauritz, L.P., 595 U.S. 178 (2022), held that a registrant's lack of knowledge may concern law or fact. You should investigate application errors before litigation because accuracy, knowledge, and materiality can require evidence beyond the certificate.

Factual Copying

A plaintiff must first prove that the defendant used the copyrighted work when creating the accused work. Examples of direct proof include an admission, source files, revision histories, copied metadata, or testimony from a participant. Most cases depend on circumstantial evidence.

Federal courts commonly permit an inference of factual copying from access and similarities probative of copying, although their terminology differs. In Batiste v. Lewis, 976 F.3d 493 (5th Cir. 2020), the Fifth Circuit explained that access requires a reasonable opportunity to view or hear the work, beyond a bare possibility or speculation. Direct delivery, dealings through an intermediary, shared creative personnel, or distribution that placed the work before the defendant can supply that proof, depending on the governing circuit and the evidence.

Probative similarity asks whether similarities support an inference that the defendant used the plaintiff's work. At this stage, a court can consider similarities in unprotectable material because the inquiry concerns copying as a historical event. Stronger proof of similarity can compensate for weaker proof of access, but even extensive access can't establish factual copying without some probative similarity.

Striking similarity supports an inference of copying without separate proof of access when the governing circuit's standard is satisfied. That standard requires more than substantial similarity. The similarities must make independent creation, coincidence, and use of common sources sufficiently implausible to support the inference.

Actionable Copying

Proof that the defendant copied something doesn't complete the claim. The plaintiff must also prove substantial similarity between protectable expression in the copyrighted work and the accused work. Copyright excludes ideas, facts, procedures, systems, methods of operation, stock elements, public domain material, and expression dictated by functional constraints.

Each circuit applies its own formulation of the substantial similarity inquiry. Fifth Circuit courts compare the works side by side from the perspective of an ordinary observer after identifying the protectable expression. Nola Spice Designs, L.L.C. v. Haydel Enterprises, Inc., 783 F.3d 527, 550, 552 (5th Cir. 2015), explained that substantiality concerns the qualitative and quantitative importance of the copied material to the plaintiff's work.

The Ninth Circuit uses an objective extrinsic test and a subjective intrinsic test, as its en banc opinion in Skidmore v. Led Zeppelin, 952 F.3d 1051 (9th Cir. 2020), explains. Second Circuit courts use an ordinary observer test, with a more discerning comparison when a work contains protected and unprotected material. For computer programs, Computer Associates International, Inc. v. Altai, Inc., 982 F.2d 693 (2d Cir. 1992), developed the abstraction, filtration, and comparison method that has influenced software cases across several circuits.

Different works require different comparisons even within the same circuit. Under a filtration analysis, a court evaluating software separates protectable code or structure from ideas, efficiency constraints, external standards, and public domain elements. With music, photographs, visual art, and written works, the parties often dispute the level of generality at which the comparison occurs. Copying a small but distinctive part can prove infringement, while copying a larger amount of unprotectable material doesn't establish infringement.

A plaintiff who defines the protected expression too broadly risks claiming an idea, while a defendant who reduces a work to isolated fragments can obscure a protected selection, arrangement, or combination. Because the controlling test depends on venue and the type of work, the pleadings, expert analysis, and comparison evidence should use the law of the circuit hearing the case.

Probative similarity and striking similarity concern whether factual copying occurred. Substantial similarity concerns whether copying of protected expression is actionable. Expert testimony can identify technical similarities, source code relationships, musical structure, or industry constraints, but it can't replace the court's legal determination of protectability or the factfinder's comparison under the governing standard. A court can decide substantial similarity as a matter of law when no reasonable jury could find actionable copying.

Defenses

Independent creation defeats infringement because copyright protects against copying. Two people can create identical expression independently without violating the Copyright Act. A defendant should preserve drafts, timestamps, source files, research materials, version histories, and testimony showing how the accused work developed.

A license authorizes the challenged use within its stated scope, including its territory, term, media formats, audience, and field of use. The parties can dispute whether conduct exceeded that scope, whether conditions on the license occurred, or whether the licensor owned the licensed rights. Written agreements, payment records, platform terms, and communications surrounding the license often determine the result.

A court deciding fair use under Section 107 considers the purpose and character of the use, the nature of the copyrighted work, the amount and substantiality used, and the effect on the potential market. Courts weigh the factors together in context. Other defenses include invalidity, lack of ownership, statute of limitations, implied license, first sale, de minimis copying, copyright misuse, common source, and scènes à faire, depending on the work and challenged conduct.

Registration Timing and Remedies

Section 412 links registration timing to statutory damages and attorney's fees. For an unpublished work, infringement that commenced before registration bars both remedies. For a published work, infringement that commenced after first publication and before registration bars both remedies unless the owner registered within three months after first publication.

For infringement that commenced before registration, the owner can file suit after registration and seek actual damages and infringer profits. Section 412 bars statutory damages and attorney's fees for that infringement unless the owner registered a published work within three months after first publication. Courts disagree over whether subsequent conduct constitutes a new infringement or continues the infringement that began before registration, so you should register valuable works promptly.

Current Copyright Office fees include $45 for an eligible electronic single application and $65 for the standard electronic application. Special handling costs an additional $800 for a claim and is limited to specified urgent circumstances, including pending or prospective litigation. On July 14, 2026, the Office submitted a proposed replacement fee schedule to Congress and announced that it seeks implementation in fall 2026. You should confirm current fees on the Copyright Office fee page before filing.

Actual Damages and Infringer Profits

Section 504(b) permits recovery of the copyright owner's actual damages and additional profits of the infringer attributable to infringement. Depending on the evidence, actual damages can include lost sales, lost license fees, price erosion, or other provable economic loss. A reasonable license fee can serve as evidence when it rests on objective market facts rather than speculation.

For infringer profits, the copyright owner must present proof of the infringer's gross revenue connected to the infringement. The infringer must prove deductible expenses and the portion of profit attributable to factors other than the copyrighted work. Revenue from an entire company or product line can be too remote when the accused use concerns only one component, so the parties should identify the revenue stream and causal connection early.

Statutory Damages and Attorney's Fees

A copyright owner who satisfies Section 412 can elect statutory damages instead of actual damages and infringer profits. Section 504(c) sets a range of $750 to $30,000 per work, permits an increase to $150,000 for willful infringement, and permits a reduction to $200 when the infringer proves innocent infringement under the statutory standard.

Section 504(c) authorizes one statutory damages award per work infringed for each infringer who is individually liable, or for multiple infringers who are jointly and severally liable. Repeated infringements of the same work by the same infringer don't multiply the award. All parts of a compilation or derivative work constitute one work for this calculation.

Section 505 permits a court to award reasonable attorney's fees to the prevailing party. In Kirtsaeng v. John Wiley & Sons, Inc., 579 U.S. 197 (2016), the Supreme Court instructed courts to give substantial weight to the objective reasonableness of the losing party's position while considering all relevant circumstances. Timely registration preserves eligibility for a plaintiff's fee request, but the court retains discretion.

Injunctions, Impoundment, and Destruction

Section 502 permits temporary and final injunctions on terms a court considers reasonable to prevent or restrain infringement. A plaintiff seeking preliminary relief must prove likely success, likely irreparable harm without an injunction, a favorable balance of equities, and consistency with the public interest. Permanent relief requires proof of irreparable injury, inadequate legal remedies, a favorable balance of hardships, and consistency with the public interest.

Section 503 permits impoundment during the action and destruction or another reasonable disposition after final judgment. A request involving inventory, servers, manufacturing materials, or source files requires precise identification and a remedy proportionate to the infringement. You should also account for preservation duties so requested relief doesn't destroy evidence needed in the case.

Secondary Liability After Cox

Contributory liability can apply to a service provider or other intermediary based on another person's direct infringement. In Cox Communications, Inc. v. Sony Music Entertainment, No. 24-171 (U.S. Mar. 25, 2026), the Supreme Court held that contributory liability requires intent that the service be used to infringe. Under Cox, a plaintiff proves that intent through affirmative inducement or by showing that the provider tailored the service to infringement, meaning the service lacks substantial or commercially significant noninfringing uses.

Knowledge that some customers will infringe, combined with insufficient efforts to prevent them, doesn't satisfy the Cox standard by itself. The Court also emphasized that the Digital Millennium Copyright Act safe harbors provide defenses and that failure to qualify for a safe harbor doesn't establish infringement. After deciding Cox, the Supreme Court vacated the Fifth Circuit's judgment in Grande Communications Networks, LLC v. UMG Recordings, Inc. and remanded for further consideration under the new standard.

Vicarious liability presents a separate theory. A plaintiff must prove the defendant's right and ability to supervise the direct infringement and a direct financial benefit from it. The pleaded theory, evidence of control, revenue connection, and available statutory defenses should match the defendant's actual role.

Filing Period and Recoverable Damages

Section 507(b) requires a plaintiff to file a civil action within three years after the claim accrued. Several circuits apply a discovery rule under which a claim accrues when the plaintiff knows or has reason to know of the injury. Martinelli v. Hearst Newspapers, L.L.C., 65 F.4th 231 (5th Cir. 2023), states the Fifth Circuit's version of that rule. The Supreme Court hasn't resolved whether the Copyright Act permits discovery rule accrual, so governing circuit law controls that issue.

In Warner Chappell Music, Inc. v. Nealy, 601 U.S. 366 (2024), the Supreme Court assumed the discovery rule applied and held that a timely claim isn't subject to a separate limit of three years on damages. A plaintiff can recover damages for older acts when the claim itself is timely under the governing accrual rule. Copyright owners should act promptly because knowledge, inquiry notice, separate acts, and continuing conduct can produce limitations disputes that depend on the facts.

Copyright Claims Board or Federal Court

The Copyright Claims Board (CCB) offers a voluntary, remote proceeding for certain copyright disputes. Total damages can't exceed $30,000 in one proceeding, and the smaller claims track caps total damages at $5,000. A respondent has 60 days after service to opt out, which sends the claimant back to federal court if the claimant wants to continue.

CCB statutory damages have separate caps. The maximum is $15,000 per work for timely registered works, subject to the $30,000 proceeding cap. For works that miss the Section 412 timing requirements, the maximum is $7,500 per work and $15,000 per proceeding. A CCB determination can include an agreement to stop infringing activity only if the respondent agrees, and judicial review is limited. You should compare the damages, discovery needs, injunction requirements, counterclaims, defendant assets, and likely litigation expense before choosing the CCB or federal court.

Evidence and Early Decisions

Copyright cases often turn on evidence that disappears quickly. A claimant should preserve registrations, deposit copies, drafts, publication dates, transfer documents, license terms, platform records, source files, analytics, revenue records, notices, and captures of the accused use. A defendant should preserve the development record, licenses, independent sources, design constraints, financial records, and communications relevant to access and intent.

Early decisions shape cost and settlement value. You should determine ownership, registration timing, protectable expression, access evidence, remedy eligibility, limitations dates, and collectability before filing. If you're defending, you should test each element separately and avoid treating visual or audible similarity as proof of legal infringement.

Copyright litigation rewards work completed before the complaint. Accurate registrations, signed transfers, preserved source files, disciplined licensing records, and timely enforcement determine what you can prove and what you can recover.