The list in Rule 404(b)(2) looks reassuring at first glance. Motive, opportunity, intent, preparation, plan, knowledge, identity, absence of mistake, lack of accident. Courts and practitioners treat it like a menu: pick one, serve it up, and the evidence comes in. The reality is more complicated. Slapping a label on other-acts evidence doesn’t end the inquiry; it starts it. You still have to survive Rule 403, and the government’s winning percentage on that balancing test is not as high as prosecutors would have you believe.
The Rule Itself
(b) Other Crimes, Wrongs, or Acts.
(1) Prohibited Uses. Evidence of any other crime, wrong, or act is not admissible to prove a person’s character in order to show that on a particular occasion the person acted in accordance with the character.
(2) Permitted Uses. This evidence may be admissible for another purpose, such as proving motive, opportunity, intent, preparation, plan, knowledge, identity, absence of mistake, or lack of accident.
(3) Notice in a Criminal Case. In a criminal case, the prosecutor must:
(A) provide reasonable notice of any such evidence that the prosecutor intends to offer at trial, so that the defendant has a fair opportunity to meet it;
(B) articulate in the notice the permitted purpose for which the prosecutor intends to offer the evidence and the reasoning that supports the purpose; and
(C) do so in writing before trial, or in any form during trial if the court, for good cause, excuses lack of pretrial notice.
The Non-Propensity Purposes (And Why the Label Isn’t Enough)
The listed purposes in Rule 404(b)(2) are examples, not an exhaustive catalog. Courts have found other acceptable purposes when the logic holds. But the word “such as” in the rule doesn’t mean “anything you can name.” The evidence has to actually fit the purpose you’re claiming.
The classic problem is intent. If the government says a defendant’s prior drug conviction proves knowledge or intent in a current drug trafficking case, that argument works only if intent is actually disputed and the prior act genuinely illuminates the mental state at issue. If the defendant is running an entrapment defense or otherwise contesting whether he knew what was in the package, prior drug activity becomes more relevant. If the defense is “I wasn’t there,” then identity is in play, not intent, and lumping in a prior conviction under the “intent” label gets you into propensity territory dressed up as something else.
Huddleston v. United States, 485 U.S. 681 (1988) is the foundational case on the admissibility standard. The Court held that Rule 404(b) evidence does not require the trial court to make a preliminary finding that the prior act actually occurred by a preponderance of the evidence before submitting it to the jury. Rather, the evidence is properly admitted if there is sufficient evidence for the jury to reasonably find that the defendant committed the prior act. This matters practically: you cannot defeat admission just by arguing the prior act is disputed. You need to focus on relevance and Rule 403.
The Rule 403 Balancing Test Is Where the Fight Actually Happens
Once a proponent identifies a non-propensity purpose, the court still has to run the Rule 403 analysis: is the probative value substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury? Courts articulate this as a high bar for exclusion, but in practice the 403 analysis is where Rule 404(b) evidence actually gets knocked out.
There are four things courts look at in this analysis that you should address directly in your briefs:
- How similar is the other act to the charged conduct? The more similar, the more the jury will use it as propensity evidence regardless of the instruction.
- How close in time? Older acts have diminished probative value on current intent or knowledge.
- How necessary is the evidence? If intent isn’t genuinely disputed, the probative value of a prior act on that issue drops sharply.
- What limiting instruction can address the prejudice? Courts lean heavily on instructions, sometimes too heavily.
In the Seventh Circuit, the courts have been relatively receptive to the government on 404(b) evidence in fraud and narcotics cases. The Ninth Circuit has been more skeptical in certain contexts, particularly where the “plan” rationale is stretched to cover conduct that just looks similar to the charged offense. Know your circuit’s tendencies and cite them.
The Pretrial Notice Requirement Has More Teeth Than It Used To
The 2020 amendments rewrote the notice requirement in Rule 404(b)(3). The old version required the prosecutor to provide notice — but only if the defendant first made a request — of the “general nature” of the evidence. The current version makes notice automatic, requires it in writing before trial, and requires that the prosecutor articulate the permitted purpose and the reasoning that supports it.
This change matters. Boilerplate government notice letters that said “the government may offer evidence of other crimes to show knowledge, intent, motive, plan, preparation, identity, and absence of mistake” are no longer sufficient. The prosecutor has to explain why a specific piece of evidence supports a specific purpose. Courts have started calling this out. If you’re on the defense side, read the government’s notice carefully and move to exclude any evidence where the notice fails to connect the dots between the act and the claimed purpose.
The common mistake defense counsel makes here is treating inadequate notice as grounds for automatic exclusion without pushing the court to enforce the specificity requirement. The rule allows the court to excuse pretrial notice for good cause, but that exception is for genuine trial surprises, not for the government’s failure to do the work beforehand.
Practical Takeaways for Both Sides
If you’re defending against a 404(b) motion in a civil case, remember the notice requirement only applies to criminal proceedings. Civil litigants fighting other-acts evidence are working entirely within Rule 403 and the non-propensity purposes, without the procedural hook of inadequate notice.
For criminal defense lawyers, the motion in limine on 404(b) evidence is not a throwaway filing. Frame your argument around two tracks: first, why the stated purpose is pretextual or not actually at issue in the case; second, why the Rule 403 balance tips toward exclusion even if the purpose is legitimate. Generic “more prejudicial than probative” arguments lose. Specific arguments about why the jury cannot compartmentalize this particular prior act given the similarity to charged conduct are much harder to brush off.
The government’s instinct is to front-load prior bad acts to make defendants look like repeat offenders. The rule exists precisely to prevent that. Push back on the reasoning, not just the conclusion.