Likelihood of confusion sits at the heart of most TTAB opposition and cancellation proceedings. While many discussions focus heavily on the DuPont factors themselves, far fewer explain how the burden of proof actually moves throughout a case and how the Trademark Trial and Appeal Board evaluates evidence under the Trademark Trial and Appeal Board Manual of Procedure. For trademark owners, applicants, and practitioners alike, understanding burden shifting is not just academic. It often determines which party prevails when the record is close.

This article takes a procedural and evidentiary look at likelihood of confusion through the lens of the TBMP, focusing on how burdens are allocated, how evidence is weighed, and why strategic record building matters from the very first pleading.

The Initial Burden of Proof in TTAB Likelihood of Confusion Cases

In any TTAB opposition or cancellation based on likelihood of confusion, the burden of proof begins squarely with the plaintiff, whether that party is an opposer or a petitioner. Under TBMP guidance and long standing Board precedent, the plaintiff must establish a prima facie case by a preponderance of the evidence.

This initial burden requires more than conclusory allegations. The plaintiff must introduce evidence supporting the relevant DuPont factors, including ownership and priority of a valid mark, similarity of the marks, relatedness of the goods or services, and overlapping channels of trade. While not every DuPont factor must be proven, the evidence must be sufficient to show that confusion is likely when the marks are used in commerce.

At this stage, the Board evaluates the record as a whole, not by tallying factors, but by assessing whether the evidence collectively supports a finding of likely confusion.

How the TBMP Treats the DuPont Factors as Flexible Evidentiary Tools

One of the most misunderstood aspects of TTAB likelihood of confusion analysis is the role of the DuPont factors themselves. The TBMP makes clear that the DuPont factors are not a rigid checklist. They are flexible considerations that guide the Board’s evaluation of the evidence presented.

Some factors may carry more weight than others depending on the record. For example, similarity of the marks and relatedness of the goods often dominate the analysis. Other factors, such as actual confusion or market interface, may be absent entirely without harming the plaintiff’s case.

This flexibility is critical when considering burden shifting. A strong showing on a few key factors can be enough to establish a prima facie case and shift the practical burden to the defendant to rebut or neutralize that showing.

When and How the Practical Burden Shifts to the Defendant

Once the plaintiff meets its initial burden, the practical burden shifts to the defendant, typically the applicant or registrant, to introduce countervailing evidence. While the ultimate burden of persuasion never leaves the plaintiff, the defendant must respond if it hopes to avoid an adverse outcome.

This is where many TTAB cases are lost. Defendants often rely on argument rather than evidence, assuming the plaintiff’s case is weak enough to fail on its own. The TBMP and Board decisions repeatedly emphasize that unsupported arguments do not rebut record evidence.

Defendants may attempt to weaken the plaintiff’s case by introducing evidence showing differences between the marks, distinct trade channels, sophisticated consumers, or widespread third party use of similar marks. When properly supported, this evidence can significantly affect how the Board weighs the DuPont factors.

Evidence Weighting and the Board’s Record Driven Analysis

Under the TBMP, the TTAB does not independently investigate facts. The Board decides cases based solely on the evidence properly made of record. This makes evidence weighting a central issue in likelihood of confusion disputes.

Not all evidence carries equal weight. For example, third party registrations alone may show conceptual weakness of a mark, but they carry less weight than proof of actual marketplace use. Similarly, testimony declarations may be persuasive, but they are often scrutinized more closely than objective documentary evidence.

The Board evaluates evidence in context. A small amount of strong evidence may outweigh a large volume of weak or irrelevant material. This is why strategic evidence selection matters more than sheer quantity.

Burden Shifting in the Context of Weak and Strong Marks

One area where burden shifting becomes particularly important is the strength of the plaintiff’s mark. When a plaintiff introduces evidence that its mark is commercially strong and distinctive, the defendant is often forced to respond with evidence of third party use or registration to show dilution of source identifying power.

If the defendant successfully demonstrates that a mark is weak in the marketplace, the Board may narrow the scope of protection afforded to that mark. This can significantly affect the likelihood of confusion analysis, especially where similarities between the marks are modest.

The TBMP supports this nuanced approach, recognizing that the strength of a mark directly influences how other DuPont factors are weighed.

Priority Evidence and Its Role in Burden Allocation

Priority is a threshold issue in TTAB likelihood of confusion cases. The plaintiff bears the burden of proving earlier use or ownership of a valid registration. Once priority is established, it is generally not revisited unless the defendant introduces evidence calling it into question.

This creates an early burden shift. Defendants who fail to challenge priority with competent evidence often lose the opportunity to contest it later. The TBMP emphasizes that stipulations, admissions, and unchallenged registrations can conclusively establish priority, streamlining the remainder of the case.

How Incomplete Records Affect Burden Shifting Outcomes

The TBMP repeatedly warns parties about the consequences of incomplete records. When a party with the practical burden fails to submit evidence on an issue, the Board may draw adverse inferences or simply give greater weight to the opposing party’s proof.

This often occurs with trade channel evidence. If the plaintiff relies on the identifications in the pleadings and the defendant introduces no limiting evidence, the Board presumes that the goods or services travel through all normal channels of trade. That presumption can be decisive.

Strategic Takeaways for TTAB Litigants

Understanding burden shifting under the TBMP changes how cases should be litigated. Plaintiffs must focus on building a clean, credible prima facie case with evidence tailored to the most influential DuPont factors. Defendants must recognize when silence is dangerous and when rebuttal evidence is essential.

Likelihood of confusion cases before the TTAB are not won by rhetoric. They are won by disciplined evidence presentation and an appreciation of how the Board weighs that evidence under established procedural rules.

Final Thoughts on Burden Shifting and TBMP Guided Advocacy

The burden shifting framework in TTAB likelihood of confusion cases reflects the Board’s evidence driven nature. While the plaintiff carries the ultimate burden, the practical realities of litigation mean that both sides must actively engage with the record.

Your brand is everything. Understanding how the TBMP shapes evidentiary burdens can make the difference between protecting your trademark and losing valuable rights. When the outcome turns on subtle distinctions, experienced TTAB advocacy becomes essential.

If you are navigating an opposition or cancellation and want to understand how your evidence will be weighed, speaking with a trademark attorney early can help you build a stronger, more strategic record.