Arnstein v. Porter: The Two-Step Copyright Infringement Test

Arnstein v. Porter, 154 F.2d 464 (2d Cir. 1946), is the Second Circuit decision that established the two-step test still used to analyze civil copyright infringement of musical and other creative works. Songwriter Ira Arnstein sued composer Cole Porter for allegedly plagiarizing his compositions, and Judge Jerome Frank’s opinion split the infringement question in two: first, did the defendant actually copy the plaintiff’s work, and second, did that copying go far enough to count as an unlawful appropriation in the ears of an ordinary listener.¹

What Arnstein Accused Porter Of

Arnstein claimed Porter had lifted themes from his compositions, including “The Lord is My Shepherd” and “A Mother’s Prayer,” to build several well-known hits:¹

Begin the Beguine
My Heart Belongs to Daddy
Don’t Fence Me In

He also alleged that Porter or people working for him had sent spies to follow him and ransack his apartment for unpublished manuscripts. Those claims put the question of how Porter could have gained access to the music squarely in dispute.¹

The Two-Step Test the Case Established

To decide whether infringement had occurred, the court set out a two-part inquiry. The plaintiff must first prove that actual copying took place. If that is shown, the analysis moves to a separate question: whether the copying reached the level of an improper or unlawful appropriation of the original expression.¹

Splitting the question this way matters because copying, on its own, is not automatically actionable. Some overlap between two works may be lawful. The second step forces the fact-finder to decide whether what was taken is significant enough to count as a legal wrong.¹

Step One: Proving Actual Copying

The first step asks whether the defendant used the plaintiff’s work when creating their own. Direct evidence, such as an admission, is rare. More commonly a plaintiff relies on circumstantial evidence: that the defendant had access to the work, meaning an opportunity to see or hear it, and that the two pieces contain similarities.¹

Where evidence of access is missing, the court said, the similarities themselves must be striking, so alike that independent creation becomes highly unlikely. When both access and similarity are present, the fact-finder weighs the whole picture to decide whether copying, rather than coincidence, best explains what happened. Expert analysis, including musicological breakdowns, is permitted at this stage to help establish that copying occurred.¹

Step Two: The Ordinary Lay Listener Standard

Once copying is established, the court turned to whether the defendant took enough protected material to be liable. That judgment, Judge Frank held, belongs to the ordinary lay hearer, not the trained musician. The question is whether the average listener would feel that the defendant appropriated what makes the original appealing to its audience.¹

Expert testimony largely drops out at this second step. Because the public is the audience for popular music, the court reasoned, technical distinctions that only a specialist would notice cannot excuse a work that sounds copied to a normal ear. Dissection by experts is treated as irrelevant to the improper-appropriation question.¹

The Summary Judgment Ruling and Outcome

The district court had thrown the case out on summary judgment for Porter. The Second Circuit reversed. Judge Frank wrote that when a case turns on the credibility of a party’s account, a jury should hear the witnesses, even if the plaintiff’s story seemed improbable on paper. Factual disputes of that kind were not for a judge to resolve before trial.¹

On remand, the case went to a jury, which rejected Arnstein’s claims. The Second Circuit affirmed that verdict, leaving Porter’s catalog intact and the two-step framework as the case’s lasting contribution to copyright law.²

1
Justia. Arnstein v. Porter, 154 F.2d 464
2
Justia. Arnstein v. Porter, 158 F.2d 795