Inverting the Inverse Ratio Rule: Leveling the Playing Field for Copyright Infringement Defendants

Photo by Chris Brignola on Unsplash

Mike Chernoff, Associate Member, University of Cincinnati Law Review

I. Introduction

In copyright infringement lawsuits, a plaintiff may circumstantially prove copying by showing that the defendant had access to the original work and that the allegedly copied work is substantially similar to that original.[1] There are many tests to determine whether works are substantially similar. The inverse ratio rule is one of those tests. It states that the degree of substantial similarity required for a finding of infringement may inversely change with the degree of access that the defendant had to the original work.[2] Recently, the Ninth Circuit abrogated its use of the inverse ratio rule in Skidmore v. Led Zeppelin, leaving the Sixth Circuit as the only circuit that still uses the inverse ratio rule.[3]

II. Copyright Infringement

The creator of a work may be eligible for copyright protection when that work is “fixed in a tangible medium of expression.”[4] This protection gives the copyright holder the exclusive right to reproduce the work, prepare derivate works, and distribute copies of the work.[5] The copyright holder may bring suit for copyright infringement when these rights are violated.[6] There are two elements needed to establish copyright infringement: (1) ownership of a valid copyright, and (2) copying of constituent elements of the work that are original.[7] If copying must be circumstantially proven, the second element must contain two further requirements of (1) access and (2) substantial similarity.[8] The requirement of access protects an alleged infringer from liability if the second work was independently created.[9] Courts have created a multitude of tests to determine what constitutes “substantial similarity.”

A. Ninth Circuit Test

The 9th Circuit uses the “total concept and feel” test by seeking the subjective evaluation of an observer to determine if the total concept and feel of the allegedly infringing work is substantially similar to the copyrighted work.[10] The Ninth Circuit expanded on this doctrine by dividing the substantially similarity analysis into an “extrinsic test” and an “intrinsic test;” both are needed to show substantial similarity to prove infringement.[11]

The extrinsic test is used to determine whether there is substantial similarity between the ideas of the two works.[12] This portion of the analysis is considered “extrinsic” because it is not dependent on the thoughts of a person, but on “specific criteria which can be listed and analyzed.”[13] Due to the analytical nature of this test, it is often appropriate to decide the result as a matter of law.[14] Examples of criteria that can be analyzed as part of the extrinsic test include the type of artwork involved, the subject matter, and the setting of the subject.[15] Dissecting the work into elements and expert testimony are appropriate for this test because of the specific nature of the inquiry.[16]

The other portion of the Ninth Circuit’s substantial similarity assessment is called the “intrinsic test.”[17] This test depends on “the response of the ordinary reasonable person” and is dependent on the trier of fact to determine the result of this test.[18] The intrinsic test considers whether the expression of the ideas in the allegedly infringing work are substantially similar to the expression of the ideas in the original work.[19] The intrinsic test is only decided if it the extrinsic test has shown substantial similarity in ideas between the two works.[20]

B. Second Circuit Tests

The Second Circuit has developed a separate test to determine if substantial similarity is present in an allegedly infringing work. The Second Circuit’s definition of substantial similarity “requires that the copying is quantitatively and qualitatively sufficient to support the legal conclusion that infringement (actionable copying) has occurred.”[21] The quantitative element of the Second Circuit’s substantial similarity definition is dependent on the amount of a copyrighted work that is copied.[22] The qualitative element is used to decide whether there has been copying of the expression in the copyrighted work.[23] The Second Circuit relies on an “abstractions test” to separate expression from idea for use in determining the qualitative element of substantial similarity.[24] The abstractions test considers the copyrighted work at different levels of generalizations to determine which elements were expressions or ideas.[25] The Second Circuit may also apply the “ordinary observer test” when comparing two works. The ordinary observer test seeks to determine whether an ordinary observer may regard the aesthetic appeal of the two works as the same.[26] The Second Circuit requires the higher standard of the “more discerning observer” in cases where the copyrighted work has elements that have been borrowed from the public domain.[27] Any of these tests could be used by a court in the Second Circuit to show that two works are substantially similar to support a finding of copyright infringement.

C. Computer Program Tests

Another example of a substantial similarity test is the “abstraction-filtration-comparison test” for computer programs.[28] This test applies the levels of abstraction test, similar to the second circuit approach above, to separate ideas from expression.[29] For this test, a court must filter the non-protectable elements of the work from the protectable material.[30] After these element have been filtered, the court then compares the two works to determine if any of the protected expression was copied.[31] The result of this comparison will determine whether the two works were substantially similar for a finding of infringement.[32] Although this test was established in the Second Circuit, other circuits have adopted this test for application in computer software infringement cases.[33]

III. The Inverse Ratio Rule

In some circuit courts, the level of substantial similarity may affect the level of access required for a finding of infringement by the “inverse ratio rule.”[34] The inverse ratio rule requires “a lower standard of proof of substantial similarity when a high degree of access is shown.”[35] This rule also allows a case for infringement in the absence of proof of access when the works are “strikingly similar.”[36]

A majority of circuits have rejected the inverse ratio rule.[37] The Second Circuit rejected the inverse ratio rule in Arc Music Corp. v. Lee stating the rule was a “fabricated principle of law.”[38] The Fifth Circuit explicitly denied adopting the inverse ratio rule in Positive Black Talk, Inc. v. Cash Money Records, Inc. despite the support the rule had seen in other circuits.[39] The Seventh Circuit has allowed a high level of similarity to suggest access, but a “lower standard of proof” has never been endorsed because of a higher level of access.[40] The Eleventh Circuit denied using the inverse ratio rule in Beal v. Paramount Pictures Corp. and stated that the rule had never been applied in the circuit.[41]

The Sixth Circuit recognizes the inverse ratio rule in copyright infringement cases. This court affirmed the use of the inverse ratio rule in Stromback v. New Line Cinema.[42] The circuit court relied on its holding in Ellis v. Diffie which recognized an inversely proportional relationship between the degrees of proof required access and substantial similarity.[43] The Ninth Circuit has also applied the inverse ratio rule, but recently reversed on this usage in Skidmore v. Led Zeppelin.[44]

IV. The Ninth Circuit’s Inverse Ratio Rule Rejection

The fact pattern of Skidmore concerned the copyrighted work of an instrumental song Taurus.[45] Taurus was written by Randy Wolfe, also professionally known as Randy California, in 1966 and 1967 while he was a guitarist for the band Spirit.[46] In December 1967, Taurus was registered as a copyright with Wolfe listed as the author.[47] One page of sheet music of Taurus was deposited, as required under the 1909 Copyright Act, which was in effect at the time.[48] Spirit released an album, including Taurus, in January 1968.[49]

Around this time, a band was formed named Led Zeppelin.[50] It was undisputed that Spirit and Led Zeppelin had performed at the same venue in at least three instances between 1968 and 1970.[51] However, there was no direct evidence that Spirit and Led Zeppelin had been on tour together or that Led Zeppelin members heard Taurus played.[52] In November 1971, Led Zeppelin released an album containing the song Stairway to Heaven.[53]

In May 2014, a co-trustee of the Randy Craig Wolfe Trust, Michael Skidmore, filed a suit against Led Zeppelin, the Led Zeppelin members, Super Hype Publishing, and the Warner Music Group Corporation, alleging direct, contributory, and vicarious copyright infringement.[54] Skidmore also claimed a “Right of Attribution-Equitable Relief-Falsification of Rock n’ Roll History,” but this claim was disposed on a motion for summary judgment.[55] Skidmore claimed the opening notes of Stairway to Heaven were substantially similar to a passage at the beginning of deposited copy of Taurus.[56] Led Zeppelin disputed ownership, access, and substantial similarity and alleged the affirmative defenses of independent creation, unclean hands, and laches.[57] After a five day trial in the Central District of California, the jury returned a verdict of no infringement.[58] The jury found Skidmore to own the copyright on Taurus and that Led Zeppelin had access to Taurus, but that the extrinsic test failed to find substantial similarity.[59] Notably, the district court did not give a jury instruction on the inverse ratio rule, despite Skidmore’s objection.[60] Skidmore filed an appeal and a panel from the Ninth Circuit vacated the judgment and remanded the case for a new trial.[61] However, the Ninth Circuit then granted a rehearing en banc.[62]

Amongst a number of challenges on appeal, Skidmore sought review of the district court’s refusal to give a jury instruction concerning the inverse ratio rule.[63] The en banc court upheld the district court’s decision, including the lack of an inverse ratio rule instruction.[64] The en banc court used this decision to abrogate the rule in the Ninth Circuit and overruled prior cases that had applied the rule.[65] The Circuit Court’s decision stated the inverse ratio rule “defies logic[…] and creates uncertainty for the courts and the parties[.]”[66] According to the court, the rule’s “checkered application” in the Ninth Circuit and the rejection of the rule by other circuits helped expose the flaws in the rule.[67] The court also stated that the inverse ratio rule improperly alters the jury’s decision by altering the burden of proof.[68]

V. Discussion

The variation of substantial similarity tests creates different effects of the laws on creators due to their location. The inverse ratio rule further complicates these standards in a way that is unfair to alleged infringers. The level of similarity that a later creator may need to consider would have an endless number of possibilities with a equal number of scenarios that could satisfy the access requirement of copying. For example, the inverse ratio rule could create different substantial similarity standards for alleged infringers that own a CD containing an allegedly copied song and alleged infringers that live in an area where the allegedly copied song receives lots of radio airplay. Although these two hypothetical alleged infringers may have created equally similar works when compared to the original, one may be found to have copied whereas the other may not under the inverse ratio rule. These changing standards are made even more unpredictable due to the differences that circuit courts use to determine substantial similarity. These varying tests make it difficult for creators to know how similar two works may be allowed to be because the applicable test of law varies by location. For creators of works, the different standards of substantial similarity combined with the inverse ratio rule create an unpredictable body of law that is unfair to past, present, and future creators.

The inverse ratio rule also decreases trial efficiency. In copyright infringement suits, a defendant may admit to having access of a work to ensure a less costly trial by only litigating the substantial similarity portion of the copying requirements. However, in jurisdictions with the inverse ratio rule, this strategy may create a more difficult standard for the alleged infringer. Admitting to a high level of access would lessen the burden for proving substantial similarity and raise the probability of a finding of infringement. Under this rule, defendants would fight to prove as little access as possible, which would raise discovery costs and increase the time spent at trial. Parties also may resist admitting to access, as the threat of litigating access may prove to be leverage in settlement discussions. Judicial efficiency would greatly benefit from the removal of the inverse ratio rule by disposing of unnecessary issues before trial.

The changing standards of substantial similarity and judicial inefficiency are reasons why the Ninth Circuit made the correct decision when they chose to discontinue use of the inverse ratio rule. As the only circuit that continues to apply the inverse ratio rule, the Sixth Circuit should also discontinue usage of the rule and create a more efficient and clear standard in copyright infringement cases.

VI. Conclusion

Against a backdrop of varying substantial similarity standards, the use of the inverse ratio rule creates an unfair application of copyright infringement laws for alleged infringers. The Ninth Circuit’s recent decision to halt the use of the inverse ratio rule will provide fairer and more efficient trials and the Sixth Circuit should follow the Ninth Circuit’s lead by disposing of the inverse ratio rule.


[1] Melville B. Nimmer & David Nimmer, Nimmer on Copyright §13.01(B).

[2] Three Boys Music Corp. v. Bolton, 212 F.3d 477, 485 (9th Cir. 2000) (citing Smith v. Jackson, 84 F.3d 1213, 1220 (9th Cit. 1996); Baxter v. MCA, Inc., 812 F.2d 421, 423, 424 n.2 (9th Cir. 1987)).

[3] Skidmore v. Led Zeppelin, No. 16-56057, 2020 U.S. App. LEXIS 7585, at *30 (9th Cir. Mar. 9, 2020).

[4] 17 U.S.C.S. § 102 (Lexis 2020).

[5] 17 U.S.C.S. § 106 (Lexis 2020).

[6] 17 U.S.C.S. § 501(a) (Lexis 2020).

[7] Feist Publ’ns, Inc. v. Rural Tel. Serv. Co., 499 U.S. 340, 361 (1991).

[8] Melville B. Nimmer & David Nimmer, Nimmer on Copyright §13.01(B).

[9] Id.

[10] Roth Greeting Cards v. United Card Co., 429 F.2d 1106, 1110 (9th Cir. 1970).

[11] Sid & Marty Krofft Television Prods. V. McDonald’s Corp., 562 F.2d 1157, 1164 (9th Cir. 1977).

[12] Id.

[13] Id.

[14] Id.

[15] Id.

[16] Id.

[17] Id.

[18] Id.

[19] Id.

[20] Id.

[21] Ringgold v. Black Entm’t Television, Inc., 126 F.3d 70, 75 (2d Cir. 1997).

[22] Id.

[23] Id.

[24] Id.

[25] Attia v. Soc’y of the N.Y. Hospital, 201 F.3d 50, 54-55 (2d Cir. 1999) (citing Nichols v. Universal Pictures Corp., 45 F.2d 119, 121 (2d Cir. 1930)).

[26] Peter Pan Fabrics, Inc. v. Martin Weiner Corp., 274 F.2d 487, 489 (2d Cir. 1960).

[27] Boisson v. Banian, Ltd., 273 F.3d 262, 272 (2d Cir. 2001).

[28] Computer Assococs. Int’l v. Altai, 982 F.2d 693, 706 (2d Cir. 1992).

[29] Id.

[30] Id. at 707.

[31] Id. at 710.

[32] Id.

[33] See, e.g., Oracle Am., Inc. v. Google Inc., 750 F.3d 1339, 1357 (Fed. Cir. 2014); Bateman v. Mnemonics, Inc., 79 F.3d 1532, 1543 n.24, 1544 (11th Cir. 1996); Gates Rubber Co. v. Bando Chem. Indus., Ltd., 9 F.3d 823, 834 (10th Cir. 1993).

[34] Melville B. Nimmer & David Nimmer, Nimmer on Copyright §13.01(D). See Stromback v. New Line Cinema, 384 F.3d 283, 293 (6th Cir. 2004).

[35] Skidmore v. Led Zeppelin, No. 16-56057, 2020 U.S. App. LEXIS 7585, at *29 (9th Cir. Mar. 9, 2020) (quoting Three Boys Music Corp. v. Bolton, 212 F.3d 477, 485 (9th Cir. 2000)).

[36] Three Boys Music Corp. v. Bolton, 212 F.3d 477, 485 (9th Cir. 2000) (citing Smith v. Jackson, 84 F.3d 1213, 1220 (9th Cit. 1996); Baxter v. MCA, Inc., 812 F.2d 421, 423, 424 n.2 (9th Cir. 1987)).

[37] Skidmore, 2020 U.S. App. LEXIS 7585 at *30 (citing Positive Black Talk, Inc. v. Cash Money Records, Inc., 394 F.3d 357, 371 (5th Cir. 2004); Reed Elsevier, Inc. v. Muchnick, 559 U.S. 154, 154 (2010); Beal v. Paramount Pictures Corp., 20 F.3d 454, 460 (11th Cir. 1994); Arc Music Corp. v. Lee, 296 F.2d 186, 187-88 (2d Cir. 1961)).

[38] Arc Music, 296 F.2d at 187.

[39] Positive Black Talk, 394 F.3d at 371-72.

[40] Peters v. West, 692 F.3d 629, 634-35 (7th Cir. 2012).

[41] Beal, 20 F.3d at 460.

[42] Stromback v. New Line Cinema, 384 F.3d 283, 293 (6th Cir. 2004).

[43] Id. (citing Ellis v. Diffie, 177 F.3d 503, 506 (6th Cir. 1999)).

[44] Skidmore v. Led Zeppelin, No. 16-56057, 2020 U.S. App. LEXIS 7585, at *30 (9th Cir. Mar. 9, 2020).

[45] Id. at *7.

[46] Id. at *7-8.

[47] Id. at *8.

[48] Id. at *8.

[49] Spirit, Allmusic, https://www.allmusic.com/album/spirit-mw0000653465 [https://perma.cc/P675-JV9Z].

[50] Skidmore, 2020 U.S. App. LEXIS 7585 at *8.

[51] Id. at *8-9.

[52] Id. at *9.

[53] Led Zeppelin IV, Allmusic, https://www.allmusic.com/album/led-zeppelin-iv-mw0000190736/releases [https://perma.cc/S2QP-CTB3].

[54] Skidmore, 2020 U.S. App. LEXIS 7585 at *9.

[55] Id. at *10-11.

[56] Id. at *10.

[57] Id.

[58] Id. at *9 n.2, *12, *15.

[59] Id. at *15.

[60] Id. at *14-15.

[61] Id. at *15-16.

[62] Id. at *16.

[63] Id. at *15, *28-29.

[64] Id. at *7.

[65] Id. at *30.

[66] Id.

[67] Id. at *30, *34-36 (citing Melville B. Nimmer & David Nimmer, Nimmer on Copyright §13.01(D)).

[68] Id. at *37.