## Facts

- Police searched a motel room connected to burglary investigations and found victims’ identification and credit cards, but not certain missing items (jewelry, silver, and gold).
- An unidentified woman called a Yarmouth police lieutenant and reported that a motor home behind 5 Jefferson Avenue contained stolen property, including jewelry, silver, and gold.
- The caller said the defendant, George Upton, had obtained the property from a person whose motel room had been searched and intended to move the motor home soon.
- The caller stated she had personally seen the stolen items and initially refused to identify herself due to fear of retaliation.
- After the officer identified the caller as Lynn Alberico (associated with Upton), she confirmed her identity and stated she had recently broken up with Upton and “wanted to burn him.”
- The officer went to the location and confirmed a motor home was parked behind the address.
- Based on an affidavit describing the tip, the officer’s corroboration, and related burglary information, a magistrate issued a search warrant for the motor home.
- The search produced items described by the caller and other incriminating evidence, leading to Upton’s convictions for burglary-related offenses.

## Issues

1. Whether the warrant affidavit established probable cause under the Fourth Amendment when evaluated under the totality-of-the-circumstances approach.
2. Whether a reviewing court must defer to a magistrate’s probable-cause determination by asking only whether there was a substantial basis for issuing the warrant.

## Decision

- The Supreme Court reversed the state high court’s judgment that had found no probable cause under the Fourth Amendment.
- The Court held that the state court misapplied Fourth Amendment doctrine by treating the informant analysis as a rigid, prong-by-prong requirement rather than a totality-of-the-circumstances inquiry.
- Applying the totality test, the Court concluded the magistrate had a substantial basis to find probable cause to search the motor home.
- The Court emphasized that reviewing courts should not decide probable cause anew but should assess whether the magistrate’s decision was supported by a substantial basis in the record.

## Legal Principles

- Probable cause for a warrant is assessed under a totality-of-the-circumstances framework; informant reliability, basis of knowledge, and police corroboration are relevant considerations, not independent prerequisites.
- A tip’s claim of firsthand observation, combined with partial corroboration of key details and consistency with known investigative facts, can support probable cause even if any single factor might be insufficient alone.
- Appellate review of a warrant is deferential: the question is whether the issuing magistrate had a substantial basis for finding probable cause, not whether the reviewing court would have issued the warrant.

## Conclusion

The Court held that the warrant to search Upton’s motor home satisfied the Fourth Amendment because, under the totality of the circumstances, the magistrate had a substantial basis to find probable cause, and the state court erred by applying an overly rigid informant analysis and insufficient deference to the magistrate’s determination.


Massachusetts v. Upton, 466 U.S. 727 (1984)