The Audience in Intellectual Property Infringement

Patents, Copyright and Trademark and Intellectual Property

Article Snapshot


Jeanne Fromer and Mark Lemley


Michigan Law Review, Vol. 112, No. 7, pp. 1251-1304, 2014


Each intellectual property (IP) regime (patent, copyright, design patent, and trademark) defines infringement differently. To find infringement, courts should require that the copy be technically similar to the original and that the sale of the copy affects the market for the original.

Policy Relevance

In hearing IP cases, courts should consider the perspective of both experts and consumers.

Main Points

  • In a case alleging the infringement of IP rights, the court asks whether the defendant’s creation is similar to the plaintiff’s original work (or brand, or idea).
  • Works that strike an expert as similar might not appear similar to a consumer, and vice versa; consumers use Velcro and zippers as substitutes, but, to an expert, they are not similar.
  • In trademark cases, courts ask the jury to decide whether a similar mark could confuse consumers in the real world; courts should use experts to detect unavoidable similarities.
  • Patent law looks to the opinion of an expert, a “person of ordinary skill in the art,” to decide if one invention infringes another’s patent.
  • Copyright law takes the best approach; courts in the Ninth Circuit consider the views of both experts and consumers in deciding whether works are substantially similar.
  • Taking the consumers’ viewpoint helps courts decide if a “copy” harms the IP owner by reducing sales of the original.
    • Using only this “market substitution” test reduces competition and harms consumers.
    • Consumers might buy plastic pipes instead of metal pipes, but that does not mean that plastic pipes infringe IP rights.
  • In future patent cases, courts could encourage innovation by adding a “market substitution” test, considering both the viewpoint of experts and the viewpoint of consumers.
    • The use of an invention in a new way should be allowed when it does not affect the market for the original, even if it is “similar” to the first invention.
    • The use of Velcro to fasten shoes does not affect the market for Velcro used in surgery.
  • In all IP cases, a finding of infringement should require both technical similarity (according to experts) and market substitution (according to consumers).


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