## Facts

- Milwaukee County detectives conducting drug-interdiction surveillance observed an older two-door Oldsmobile with California plates in a motel parking lot.
- A registration check connected the vehicle to a person with a name matching the motel registry, which showed a late-night arrival without reservations.
- Law enforcement ran names through a DEA database indicating prior drug-trafficking associations.
- Officers used a drug-sniffing dog and later conducted a warrantless search of the vehicle, including removal of an interior panel.
- Officers discovered approximately two kilograms of cocaine hidden inside the vehicle.
- Petitioners pleaded guilty to possession of cocaine with intent to distribute, preserving their right to appeal the denial of their motion to suppress the evidence.

## Issues

1. What is the proper standard of appellate review for the ultimate determinations of reasonable suspicion to stop and probable cause to conduct a warrantless search?
2. Must appellate courts review these Fourth Amendment determinations de novo, or defer to trial courts under a clear-error or similarly deferential standard?

## Decision

- The Supreme Court held that the ultimate questions of reasonable suspicion and probable cause are reviewed de novo on appeal.
- The Court reaffirmed that appellate courts review findings of historical fact only for clear error.
- Reviewing courts must give due weight to reasonable inferences drawn from the facts by trial judges and law enforcement officers.
- The Court vacated the judgment of the Seventh Circuit and remanded for application of the proper standard of review.
- Justice Scalia dissented, arguing that these determinations are sufficiently fact-bound to warrant more deferential appellate review.

## Legal Principles

- Reasonable suspicion and probable cause determinations present mixed questions of law and fact requiring independent (de novo) appellate review of the ultimate constitutional question.
- Historical facts found by the trial court are reviewed for clear error, not de novo.
- Appellate courts should give due weight to inferences drawn from historical facts by trial judges familiar with local conditions and by experienced police officers.
- De novo review of the ultimate question promotes uniformity and clearer Fourth Amendment rules while preserving deference to trial-level factfinding.

## Conclusion

The Court required independent appellate review of whether established facts amount to reasonable suspicion or probable cause, while preserving clear-error review for historical facts and according due weight to trial-court and police inferences, and it remanded for reconsideration under that framework.


Ornelas v. United States, 517 U.S. 690 (1996)