# MBE Evidence Prior Bad Acts: MIMIC Non-Propensity Trap

Canonical: https://www.barprepplay.com/mbe/evidence/character-evidence-mimic-prior-bad-acts/
Subject: Evidence
Byline: BarPrepPlay
Last reviewed: April 21, 2026

## Fact pattern

Daria is on trial for the armed robbery of the Westwood Credit Union on March 4. The robber wore a yellow ski mask, used a chrome revolver with a wooden grip, and forced the teller to hand over cash in a cloth bag stamped with a faded paw-print logo. The prosecution offers evidence that, two years earlier, Daria pleaded guilty to robbing a different credit union in another county. In that earlier robbery, the robber wore a yellow ski mask, used a chrome revolver with a wooden grip, and used a cloth bag stamped with the same faded paw-print logo. Daria objects under FRE 404(b), arguing the prior robbery is inadmissible character evidence. The prosecution responds that the prior act is offered to show identity, not propensity.

## Quick answer

The court should admit the prior robbery for the limited purpose of proving identity, give a limiting instruction on request, and bar the jury from using the prior act as propensity evidence. Under FRE 404(b)(1), evidence of a prior crime, wrong, or other 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. Under FRE 404(b)(2), the same evidence may be admissible for non-propensity purposes — commonly summarized by the MIMIC mnemonic: motive, intent, mistake (absence of), identity, and common plan or scheme. To use prior-act evidence for identity, the proponent must show a sufficiently distinctive modus operandi — a signature so unusual that it acts as a fingerprint linking the two acts. The proponent must also satisfy FRE 403 balancing and, on request, the court must give a limiting instruction under FRE 105.

## Issue

May the prosecution introduce Daria's prior credit-union robbery to prove that she is the robber of the Westwood Credit Union, even though it would be excluded as propensity evidence?

## Rule

Under FRE 404(b)(1), evidence of a prior crime, wrong, or other 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. Under FRE 404(b)(2), the same evidence may be admissible for non-propensity purposes — commonly summarized by the MIMIC mnemonic: motive, intent, mistake (absence of), identity, and common plan or scheme. To use prior-act evidence for identity, the proponent must show a sufficiently distinctive modus operandi — a signature so unusual that it acts as a fingerprint linking the two acts. The proponent must also satisfy FRE 403 balancing and, on request, the court must give a limiting instruction under FRE 105.

## Application

The prosecution offers the prior robbery to prove identity, not to argue that Daria is a habitual robber. The two crimes share an unusually specific signature: the same yellow ski mask, the same chrome revolver with a wooden grip, and a cloth bag stamped with the same faded paw-print logo. None of those features individually would be especially distinctive — yellow ski masks are not unique — but in combination, and especially with the paw-print bag, the cluster forms a signature that is highly probative of identity. The probative value is substantial; the prejudicial effect of jurors thinking Daria is a "robber type" is real but can be mitigated by a limiting instruction telling the jury to consider the prior act only on identity, not on character. Under FRE 403 balancing, the probative value of the modus-operandi match outweighs the unfair prejudice. Daria is entitled to a limiting instruction under FRE 105 if she requests one.

## Conclusion

The court should admit the prior robbery for the limited purpose of proving identity, give a limiting instruction on request, and bar the jury from using the prior act as propensity evidence.

## Numbered reasoning steps

1. Identify the proponent's purpose — propensity (barred under 404(b)(1)) or one of the MIMIC purposes (allowed under 404(b)(2))?
2. For identity, evaluate whether the modus operandi is distinctive enough to function as a signature.
3. Run FRE 403 balancing — probative value vs unfair prejudice, confusion, or waste of time.
4. Address any required notice under FRE 404(b)(3) for criminal cases.
5. On request, provide a FRE 105 limiting instruction restricting the jury's use of the evidence.

## Why wrong answers fail

- The prior robbery is admissible because it shows Daria has a propensity for armed robbery.: Propensity is the precise inference FRE 404(b)(1) prohibits. Admissibility must rest on a non-propensity purpose like identity.
- The prior robbery is inadmissible because all prior bad acts are barred under FRE 404(b).: FRE 404(b)(2) allows prior acts for MIMIC purposes — motive, intent, absence of mistake, identity, and common plan or scheme.
- The prior robbery is admissible only after Daria takes the stand and her credibility is at issue.: That confuses 404(b) with 608/609 impeachment rules. Identity evidence under 404(b)(2) is admissible in the case-in-chief without a credibility predicate.
- The prior robbery is admissible only if Daria received notice at least 14 days before trial.: FRE 404(b)(3) requires reasonable notice in criminal cases, but the rule does not impose a fixed 14-day floor — the deadline turns on the court's scheduling order.

## Issue-spotting checklist

- Pin down the proponent's articulated purpose before debating admissibility.
- For identity, look for a distinctive cluster of details — a single common feature is rarely enough.
- Run FRE 403 balancing explicitly; do not assume probative value automatically wins.
- Confirm the criminal-case notice obligation under FRE 404(b)(3).
- Request a FRE 105 limiting instruction to confine the jury's use to the proper purpose.

## Primary law and source anchors

- **Federal Rule of Evidence 404(b)**: Prior-act evidence inadmissible for propensity, admissible for non-propensity purposes (MIMIC).
- **Federal Rule of Evidence 403**: Balancing of probative value against unfair prejudice and other countervailing concerns.
- **Federal Rule of Evidence 105**: Court must give a limiting instruction on request when evidence is admissible for one purpose but not another.
- **Huddleston v. United States, 485 U.S. 681 (1988)**: No preliminary finding of conditional fact is required; the jury must be able to find the prior act by a preponderance.

## 3-question quiz teaser

1. Which is NOT a permissible non-propensity purpose under FRE 404(b)(2)?
  - Motive
  - Identity through modus operandi
  - General disposition to commit the charged crime
  - Absence of mistake
2. For modus-operandi identity evidence to be admissible, the prior act must:
  - Be a felony of the same statutory class
  - Have a sufficiently distinctive signature linking it to the charged crime
  - Have occurred within the last 12 months
  - Have resulted in a prior conviction
3. What instruction protects the defendant when 404(b) evidence is admitted?
  - A FRE 403 balancing instruction
  - A FRE 105 limiting instruction directing the jury to use the evidence only for the permitted purpose
  - A FRE 803 hearsay-exception instruction
  - A Sixth Amendment confrontation instruction

## Related pages

- [MBE Evidence Hearsay Exception Sample Question + Ruling](https://www.barprepplay.com/mbe/evidence/hearsay-excited-utterance/)
- [MBE Criminal Law Mens Rea Trap: Burglary vs Larceny](https://www.barprepplay.com/mbe/criminal-law/burglary-larceny-mens-rea-trap/)

## Gated app actions

- [Take the 3-question quiz](https://www.barprepplay.com/?seo_slug=character-evidence-mimic-prior-bad-acts&seo_action=quiz)
- [Open a related Evidence drill](https://www.barprepplay.com/?seo_slug=character-evidence-mimic-prior-bad-acts&seo_action=drill)
- [Found an issue?](https://www.barprepplay.com/?seo_slug=character-evidence-mimic-prior-bad-acts&seo_action=report)