## Facts

- A Border Patrol agent operated near a checkpoint on U.S. Highway 191 in a remote area of southeastern Arizona close to the U.S.–Mexico border, where sensors monitored little-used roads associated with smuggling.
- In January 1998 around 2:15 p.m., a sensor alerted to a vehicle on a lightly traveled backroad used to bypass the checkpoint.
- The agent located a minivan on an unpaved road and observed conduct he considered unusual: the van slowed sharply, the driver sat rigidly, and the driver avoided acknowledging the agent.
- The agent saw children in the rear with knees elevated as if their feet rested on something on the floor.
- When the agent drove alongside, the children waved in an unusual manner, and the driver signaled and turned onto the last available road that would avoid the checkpoint.
- A registration check linked the minivan to an address in Douglas associated with heavy narcotics trafficking.
- The agent stopped the minivan, obtained consent to search, and discovered more than 100 pounds of marijuana.
- The district court denied a suppression motion, finding reasonable suspicion; the Ninth Circuit reversed by giving little or no weight to several factors; the Supreme Court reviewed and reversed.

## Issues

1. Whether the Fourth Amendment permits an investigatory vehicle stop based on reasonable suspicion derived from the totality of circumstances when individual observations may have innocent explanations.
2. Whether an appellate court may discount observed factors one-by-one as entitled to little or no weight, rather than assessing their cumulative effect and giving due weight to trained officer inferences and district court findings.

## Decision

- The Supreme Court unanimously reversed the Ninth Circuit and upheld the stop.
- The Court held that, considering the totality of the circumstances and giving due weight to the agent’s inferences and the district court’s assessment, the agent had reasonable suspicion that criminal activity was occurring.
- The Court rejected the Ninth Circuit’s factor-by-factor discounting approach as inconsistent with Fourth Amendment precedent governing reasonable suspicion.

## Legal Principles

- Reasonable suspicion is determined by evaluating the totality of the circumstances to decide whether the officer had a particularized and objective basis for suspecting wrongdoing.
- Officers may draw inferences and deductions from cumulative information based on experience and specialized training; reviewing courts must give due weight to those inferences and to local trial-court factfinding.
- Courts may not conduct a “divide-and-conquer” analysis that treats each observation as irrelevant solely because it can be explained innocently.
- Reasonable suspicion is a commonsense, nontechnical standard and is not reducible to a rigid checklist of permitted or forbidden factors.

## Conclusion

The Court held that an officer may stop a vehicle when multiple observations—each possibly innocent alone—collectively create reasonable suspicion under the Fourth Amendment, and appellate courts must assess the cumulative force of the circumstances rather than discarding factors in isolation.


United States v. Arvizu, 534 U.S. 266 (2002)