## Facts

- Bryan Commanche, a Mescalero Apache tribal member, fought with Cullen Kaydahzinne at a June 11, 2005 feast on the Mescalero reservation in New Mexico.
- The conflict began after Kaydahzinne (larger than Commanche) confronted Commanche near Kaydahzinne’s girlfriend and struck Commanche, who fell; a broader fight followed.
- Commanche used a box cutter during the altercation; Kaydahzinne and Irwin Apachito suffered serious lacerations.
- Commanche admitted cutting with the box cutter but claimed self-defense against a larger, aggressive opponent.
- The government charged Commanche with two counts of assault resulting in serious bodily injury, 18 U.S.C. §§ 1153 and 113(a)(6), and two counts of assault with a dangerous weapon, 18 U.S.C. § 113(a)(3).
- Before trial, the government sought to introduce evidence of two prior aggravated battery convictions involving sharp cutting objects, arguing admissibility under Rule 404(b) (intent; rebutting that the box cutter was merely a tool) and Rule 609(a)(1) (impeachment if Commanche testified).
- The district court admitted testimony describing the underlying facts of the prior convictions.
- The jury convicted Commanche on the two serious-bodily-injury counts and acquitted him on the two dangerous-weapon counts.

## Issues

1. Whether prior aggravated battery convictions involving sharp cutting instruments were admissible under Federal Rule of Evidence 404(b) to prove intent (and relatedly to suggest the box cutter was carried as a weapon), where the inference to intent depended on first inferring violent character and conformity.
2. Whether, under Federal Rule of Evidence 609(a)(1), the government could impeach Commanche with not only the fact of the prior felony convictions but also testimony about the detailed underlying conduct.

## Decision

- The Tenth Circuit reversed and remanded for a new trial.
- The court held the district court abused its discretion by admitting the underlying factual details of the prior aggravated battery convictions under Rule 404(b) because the government’s theory required an impermissible propensity inference as a predicate to intent.
- The court held the district court also erred under Rule 609(a)(1) by allowing detailed testimony about the facts of the prior convictions rather than limiting impeachment to the fact and general nature of the convictions (and related permissible basics).
- The court found the evidentiary errors were not harmless given the centrality of intent and self-defense and the substantial risk that the prior-acts evidence influenced the verdict.

## Legal Principles

- Rule 404(b) does not permit admission of prior bad acts as “intent” evidence when intent is relevant only if the jury first infers a character trait (e.g., propensity for violence) and then infers conduct in conformity with that trait in the charged offense.
- A permissible Rule 404(b) label (such as “intent”) does not cure evidence whose logical relevance depends on a forbidden propensity step.
- Under Rule 609(a)(1), impeachment by prior felony conviction is generally limited to the fact of conviction and its general nature (and other basic permissible information); the detailed circumstances underlying the conviction are ordinarily inadmissible because they risk functioning as substantive propensity evidence.
- When improperly admitted prior-acts evidence bears directly on a disputed self-defense/intent theory and is highly prejudicial, reversal is required if the error is not harmless.

## Conclusion

The Tenth Circuit ordered a new trial because the government introduced prior violent-act details that could affect the jury’s view of Commanche’s intent and self-defense only through forbidden propensity reasoning under Rule 404(b), and because the same details exceeded the narrow scope of impeachment permitted by Rule 609(a)(1).


United States v. Commanche, 577 F.3d 1261 (10th Cir. 2009)