## Facts

- Fernando Vizcarra-Martinez was charged with (1) conspiring to possess hydriodic acid, a listed chemical, knowing or having reasonable cause to believe it would be used to manufacture methamphetamine, and (2) possessing hydriodic acid with that knowledge or reasonable cause to believe.
- He was stopped while transporting chemicals connected to the alleged methamphetamine-manufacturing scheme.
- During the encounter, officers found a small amount of methamphetamine on his person that the government characterized as a personal-use amount.
- The government presented no evidence that Vizcarra-Martinez manufactured that methamphetamine or obtained it from any alleged coconspirator.
- Before trial, Vizcarra-Martinez moved to exclude evidence of the personal-use methamphetamine; the district court admitted it as “other act” evidence under Federal Rule of Evidence 404(b) to prove knowledge.
- At trial, the key dispute was whether Vizcarra-Martinez knew the hydriodic acid would be used to manufacture methamphetamine.
- A jury convicted him on both counts; he appealed.

## Issues

1. Whether evidence of possessing a personal-use amount of methamphetamine was admissible as intrinsic evidence or under Federal Rule of Evidence 404(b) to prove knowledge in a listed-chemical conspiracy and possession case.
2. Whether, if erroneously admitted, the error was harmless.
3. Whether the evidence was sufficient to support the convictions and whether the vehicle search violated the Fourth Amendment.

## Decision

- The Ninth Circuit reversed the convictions and remanded.
- The court held the personal-use methamphetamine evidence was not intrinsic to the charged offenses and therefore was subject to Rule 404(b).
- The court held the evidence was improperly admitted under Rule 404(b) because its probative value on knowledge was minimal absent a concrete link to the charged scheme.
- The court further held that any marginal probative value was substantially outweighed by unfair prejudice under Rule 403.
- The court concluded the error was not harmless because knowledge was central and the improper evidence risked influencing the jury through forbidden character reasoning.
- The court rejected challenges to the sufficiency of the evidence and the legality of the vehicle search, but did not reach remaining evidentiary and sentencing issues given the reversal.

## Legal Principles

- Rule 404(b) bars “other acts” evidence offered to prove propensity; when offered for knowledge or intent, the evidence must have a specific, non-propensity connection to a material issue in the charged offense.
- Personal drug use, without evidence linking the drugs to the charged conspiracy or transaction, is generally weak proof of knowledge of a separate manufacturing or precursor-chemical offense and risks an impermissible propensity inference.
- Evidence is “intrinsic” (often described as “inextricably intertwined”) only when it is part of the charged transaction or necessary to present a coherent account of the charged crime; otherwise it must satisfy Rule 404(b) and Rule 403.
- Under Rule 403, evidence with slight probative value may be excluded when it carries a substantial risk that the jury will convict based on moral disapproval or character assumptions.
- Erroneous admission of other-acts evidence is reversible when the contested element (here, knowledge) is central and the improper evidence may have affected the verdict.

## Conclusion

The Ninth Circuit reversed and remanded because admitting evidence of Vizcarra-Martinez’s personal-use methamphetamine improperly invited propensity reasoning, was not intrinsic to the listed-chemical offenses, failed Rule 404(b) and Rule 403, and was not harmless given the disputed knowledge element.


United States v. Vizcarra-Martinez, 66 F.3d 1006 (9th Cir. 1995)