Trademark Litigation – Proving Likelihood of Confusion

In trademark litigation, it is the plaintiff’s burden to plead and prove validity of the trademark and infringement by defendant.  For trademark infringement, the test is “likelihood of confusion.”  The likelihood of confusion test for trademark infringement is used in both common-law and also statutory infringement.  What exactly is the likelihood of confusion test?  Simply put, ask these three questions with respect to the affiliation with the senior user of the mark:  1) Is a defendant’s use of the mark likely to cause confusion?  2) Is defendant’s use likely to cause mistake?  3) Does defendant’s use deceive?  If the answer is  “yes” to any of these questions, there may be likelihood of confusion and trademark infringement.

Federal courts, state courts and the Patent and Trademark Office (PTO) all use the likelihood of confusion test to measure trademark infringement.  There are a number of factors considered by the courts when determining likelihood of confusion, and the factors and application differ in the various federal circuit courts.  In fact, the likelihood of confusion test is criticized as indefinite and unpredictable.  Some argue that the test can invite costly trademark litigation and even inappropriately limit valuable use of a mark.  But most state courts, Illinois included, rely on the federal court precedent regarding likelihood of confusion and trademark infringement.

Damage to the plaintiff (trademark owner) is presumed, and a plaintiff need not plead or prove actual damage for a trademark infringement case.  This is because injury to a trademark owner is presumed in trademark infringement cases, which makes sense because once there is likelihood of confusion, the assumption is that the trademark owner’s reputation is no longer in his own hands—but that of the infringer.

Who Must Be Confused?

For trademark infringement and under the likelihood of confusion test, who is confused?  It is consumers or buyers.  How many consumers or buyers must be confused?  Applicable cases describe an “appreciable” or “substantial” number of buyers to be confused by a similar mark for trademark infringement.  See for example Scarves by Vera, Inc. v. Todao Imports, Ltd., 544 F.2d 1167, 192 U.S.P.Q. 289 (2d Cir. 1976) and McGregor-Doniger, Inc. v. Drizzle, Inc., 599 F.2d 1126, 202 U.S.P.Q. 81 (2d Cir. 1979).  A number of federal cases discuss and attempt to define what “appreciable” or “substantial” should mean, which seems to be determined on a case-by-case basis depending on the specific facts of each case.  Apparently, majority of consumers is not required and even a small number of deceived or confused consumers will suffice for likelihood of confusion.

How to Prove Likelihood of Confusion in Court

Likelihood of confusion is considered to be an issue of fact.  An issue of fact is a litigation term to describe a dispute regarding a material fact in a case that is raised by the pleadings and that must be resolved by a decision of the court or jury.  An issue of fact requires a resolution of the factual dispute.  The court or jury considers and evaluates the evidence presented in order to make the decision.  So for likelihood of confusion, the court or jury will consider the facts presented by the lawyers and witnesses and make their decision as to whether likelihood of confusion exists in a particular case.  The most common forms of evidence presented in trademark infringement cases to determine likelihood of confusion are (1) survey evidence, (2) evidence of actual confusion and (3) arguments based on clear inference after comparing conflicting marks.

Expert testimony can also be important in proving likelihood of confusion, mistake or deception and is often helpful to juries and judges.  Expert opinions will typically not be allowed on the ultimate issue of whether or not there is confusion.  For trademark infringement cases, expert testimony is used to opine on the factual factors used to determine the ultimate issue of confusion and whether or not there is a valid trademark.  Each federal circuit has approximately eight factors that are considered in determining confusion, so expert testimony can be critical in helping to explain and apply the factors to the facts of a particular trademark infringement case.  An experienced trademark expert can testify on how a mark is evaluated for strength, significance of similarities, descriptiveness, among other matters.  Experts in trademark cases can also testify on the meaning of terms like distinctive, generic, secondary meaning, and other common trademark-related terms.


In conclusion, for trademark infringement, a mere possibility of consumer confusion is not sufficient.  The test for trademark infringement requires likely or “probable” confusion.  The determination of likelihood of confusion requires the consideration of a number of factors by the court and/or jury.  Some of those factors include who is confused and how many are confused, among others.  Evidence will be presented to the court, as well as expert testimony regarding the application of the factors, which differ slightly between the federal circuits.

Contact our law firm today to discuss likelihood of confusion, related trademark litigation issues or to discuss your trademark dispute.  Our Chicago trademark attorneys and litigation attorneys handle cases in state and federal courts throughout Illinois, including Cook, DuPage, Kane and Will Counties.  For additional information about trademarks, consumer protection, unfair competition or deceptive trade practices, please call or send us an email.

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