## Facts

- Juan A. Benavidez-Benavidez attempted to enter the United States at the Lukeville, Arizona port of entry in a van with a passenger.
- During primary inspection, he reported losing his border crossing card in Mexico, requested directions to reinstate his driver’s license, and denied bringing anything into the country.
- Customs agents became suspicious after noting the van’s unusual density and a strong air-freshener-like odor.
- Agents discovered 76 bundles of marijuana (about 169 pounds) concealed in the van’s doors and walls.
- A customs agent interviewed Benavidez; the interview was not recorded and its substance was disputed at trial.
- The agent testified that Benavidez first offered an implausible account about receiving the van from a church organization and later admitted he knowingly transported marijuana to Phoenix in exchange for ownership of the van.
- Benavidez denied confessing or stating he knew about the marijuana.
- Before trial, Benavidez took a polygraph and sought to introduce results supporting that he did not admit knowledge of the marijuana to the agent; the government did not stipulate to admissibility.
- After an evidentiary hearing, the district court excluded the polygraph evidence under Federal Rules of Evidence 403, 702, and 704(b); Benavidez was convicted and appealed.

## Issues

1. Whether the district court abused its discretion by excluding unstipulated polygraph evidence after a Daubert hearing under Federal Rules of Evidence 702 and 403.
2. Whether admitting a polygraph examiner’s opinion that the defendant was truthful in denying knowledge of marijuana would violate or implicate Federal Rule of Evidence 704(b) by effectively addressing the defendant’s mental state.

## Decision

- The Ninth Circuit affirmed the conviction.
- The court held the district court acted within its discretion in excluding the unstipulated polygraph evidence.
- The court concluded the district court properly applied Daubert and the Federal Rules of Evidence, and that Rule 403 provided an adequate, independent basis for exclusion.

## Legal Principles

- Polygraph evidence is not categorically admissible in federal criminal trials; it must satisfy Rule 702’s reliability and helpfulness requirements under Daubert.
- Even if relevant, polygraph evidence may be excluded under Rule 403 when its probative value is substantially outweighed by the risk of unfair prejudice, jury confusion, or misleading the jury, including the danger jurors will give polygraph results excessive weight.
- Expert testimony that a defendant was truthful in denying conduct tied to an element of the offense can implicate Rule 704(b) because it risks communicating an expert view on the defendant’s knowledge or intent.
- Trial courts have substantial discretion in evidentiary gatekeeping decisions, particularly where they conduct a detailed admissibility hearing and provide concrete Rule 403 and Rule 702 reasons for exclusion.

## Conclusion

The Ninth Circuit upheld the exclusion of an unstipulated defense polygraph because the district court reasonably found, after a full admissibility hearing, that the evidence posed a substantial risk of misleading jurors and intruding on credibility and mental-state determinations reserved to the jury, making exclusion proper under Rules 403, 702, and 704(b).


United States v. Benavidez-Benavidez, 217 F.3d 720 (9th Cir. 2000)