Arnstein v. Porter: The Two-Step Framework Behind Every Substantial Similarity Test
How the Second Circuit's 1946 split between proof of copying and improper appropriation built the framework every music infringement trial still follows.
Copyright remedies are an architecture, not a number. Once liability is established, the Copyright Act hands the plaintiff a choice between compensation and a statutory award: either actual damages plus the infringer’s attributable profits under 17 U.S.C. § 504(b), or statutory damages of $750 to $150,000 per work under § 504(c). Injunctions, impoundment, and attorney’s fees sit alongside that election as separate levers.
The election is the center of gravity. It explains why a plaintiff whose provable losses are $400 can still recover five figures, and why registration timing, discussed below, quietly determines the size of most copyright disputes before anyone files a complaint.
Feist Publications, Inc. v. Rural Telephone Service Co. (1991) states the prima facie case in two elements: ownership of a valid copyright, and copying of constituent elements of the work that are original.
Ownership is usually the easy half. A registration certificate made before or within five years after first publication is prima facie evidence of validity and of the facts stated in it under § 410(c), which shifts the burden to the defendant to attack the copyright.
Copying is the contested half, and it is almost never proven directly. Courts allow it to be inferred from access plus substantial similarity: the defendant had a reasonable opportunity to encounter the work, and the two works share protected expression to a degree an ordinary observer would notice. Where similarity is so close that coincidence and independent creation are not plausible, some courts permit striking similarity to carry the inference of access on its own. The second element does real filtering work, because it protects expression rather than ideas, facts, or scenes that flow inevitably from a subject.
Section 504(b) lets the owner recover actual damages and any profits of the infringer attributable to the infringement, to the extent those profits are not already counted in the damages figure. That last clause is the anti-double-counting rule: a sale the plaintiff would have made and did not counts once, not twice.
Actual damages typically take one of two shapes: lost sales or licensing revenue the owner would have earned, or the fair market value of a license the infringer should have bought. The second theory is common in photography and music cases, where the plaintiff’s real loss is the unpaid license fee.
The profits half carries a distinctive burden-shifting rule. The plaintiff is required to prove only the infringer’s gross revenue. The infringer then bears the burden of proving its deductible expenses and the elements of profit attributable to factors other than the copyrighted work. This is a meaningful advantage. A defendant who kept sloppy books, or who cannot separate the value of the infringed work from the value of its own brand and distribution, may find the entire revenue figure on the table.
Under § 504(c) the owner may elect statutory damages at any time before final judgment, which means the plaintiff can watch the evidence develop and switch if actual damages disappoint.
The ranges:
The unit matters more than the range. Awards are per work infringed, not per act of infringement, and all parts of a compilation or derivative work count as one work. Ten thousand unauthorized downloads of a single song produce one statutory award against a given defendant; one unauthorized use of ten photographs produces ten.
Feltner v. Columbia Pictures Television, Inc. (1998) added a constitutional wrinkle: the Seventh Amendment gives either party the right to a jury trial on the amount of statutory damages, not merely on liability. Judges no longer set the number alone when a jury is demanded, which is why headline verdicts in file-sharing and music cases have sometimes landed far above what any court would have chosen.
Two sections quietly control the whole remedy picture, and neither is about the merits.
Section 411(a) makes registration a precondition to filing an infringement suit for U.S. works. Fourth Estate Public Benefit Corp. v. Wall-Street.com (2019) resolved a circuit split by holding that registration “has been made” only when the Copyright Office has acted on the application by registering the copyright, not when the owner submits it. Filing an application is not enough.
Section 412 is the harsher one. Statutory damages and attorney’s fees are unavailable for any infringement of an unpublished work that began before registration, or for infringement of a published work that began after first publication and before registration, unless registration happened within three months of publication. Miss that window and the plaintiff is confined to actual damages and profits, which in most individual creator cases means the case is not economically worth bringing. The gate closes before the infringement occurs, which is why prompt registration is the single highest-leverage act in copyright practice.
Attorney’s fees. Section 505 permits the court, in its discretion, to award full costs and a reasonable attorney’s fee to the prevailing party, on either side. Kirtsaeng v. John Wiley & Sons, Inc. (2016) held that a court should give substantial weight to the objective reasonableness of the losing party’s position, while still considering the totality of circumstances, including litigation misconduct and the need to deter overaggressive claims. A defendant who wins on a close question is less likely to collect fees than one who defeated a baseless claim.
Injunctions. Section 502 authorizes injunctions on terms the court deems reasonable. Since eBay Inc. v. MercExchange, L.L.C. (2006), which the courts of appeals have applied to copyright, there is no presumption of irreparable harm from a finding of infringement. The plaintiff must satisfy the traditional four-factor equitable test. Section 503 separately allows impoundment and destruction of infringing copies and of the means for making them.
Time. Section 507(b) requires a civil action to be commenced within three years after the claim accrued. Most circuits apply a discovery rule, starting the clock when the owner discovered or should have discovered the infringement. Petrella v. Metro-Goldwyn-Mayer, Inc. (2014) held that laches cannot bar a damages claim brought inside that window, since Congress already set the time limit. Warner Chappell Music, Inc. v. Nealy (2024) closed the follow-on question: where a claim is timely under the discovery rule, there is no separate three-year lookback cap on damages. The Court assumed without deciding that the discovery rule applies at all, so that premise remains formally open.
How much can you get for copyright infringement? A plaintiff elects either actual damages plus the infringer’s attributable profits under 17 U.S.C. § 504(b), or statutory damages under § 504(c). Statutory damages run from $750 to $30,000 per work infringed, rising to as much as $150,000 per work if the infringement was willful and dropping to as little as $200 if the infringer proves it was innocent. Attorney’s fees and costs are separately available under § 505 at the court’s discretion.
What must a plaintiff prove to win a copyright infringement case? Two things, per Feist Publications v. Rural Telephone Service (1991): ownership of a valid copyright, and copying of constituent elements of the work that are original. Copying is almost never proven by a confession, so plaintiffs show it circumstantially through the defendant’s access to the work plus substantial similarity between the works, or through similarity so striking that independent creation is not a plausible explanation.
Are statutory damages awarded per infringement or per work? Per work infringed, not per act of infringement. One award covers all infringements of a single work by a single defendant or by jointly liable defendants, no matter how many downloads, copies, or performances occurred. All parts of a compilation count as one work under § 504(c)(1). A defendant who copies one photograph ten thousand times faces one statutory award; a defendant who copies ten photographs once faces ten.
What is the statute of limitations for copyright infringement? Three years from when the claim accrued, under 17 U.S.C. § 507(b). Most circuits apply a discovery rule, so the clock starts when the plaintiff discovered or reasonably should have discovered the infringement. In Warner Chappell Music v. Nealy (2024) the Supreme Court held that a claim timely under that rule carries no separate three-year cap on damages, so recovery can reach back to infringements that are decades old.
Going further: How copyright statutory damages are calculated .
This page is general legal information, not legal advice, and it does not create an attorney-client relationship.
How the Second Circuit's 1946 split between proof of copying and improper appropriation built the framework every music infringement trial still follows.
The Supreme Court held that an infringer's profits must be apportioned so the copyright owner recovers only the share attributable to the infringed material.
In Warner Chappell Music, Inc. v. Nealy (May 9, 2024), a 6-3 Supreme Court held that a copyright owner with a timely claim may recover damages for infringement no matter how long ago it occurred, while pointedly leaving the validity of the discovery rule itself undecided.
The Supreme Court held that prevailing copyright defendants and plaintiffs must be treated alike when courts award attorney's fees under Section 505: a discretionary, evenhanded standard.
The Supreme Court held that the Seventh Amendment guarantees a jury trial on statutory copyright damages (including the amount itself), reshaping how infringement awards are decided.
A unanimous Supreme Court held that distributing a device with the object of promoting its use to infringe copyright creates liability for the resulting infringement by users.
The Ninth Circuit held that Napster was liable for contributory and vicarious copyright infringement because it knew of infringing files and could police its central index but did not.
The Supreme Court held that the equitable defense of laches cannot bar a copyright damages claim filed within the Act's three-year limitations period, a decision that reoriented how delay is policed in infringement remedies.
On the second trip to the Supreme Court, Kirtsaeng resolved how district courts should weigh a losing party's litigating position when awarding attorneys' fees under § 505 of the Copyright Act.