## Facts

- Federal prosecutors charged Nathaniel Pembrook and others with offenses arising from two armed robberies of Michigan jewelry stores on April 22, 2014.
- Investigators obtained historical cell-site location information (CSLI) from cellular providers for phones associated with certain defendants.
- The CSLI reflected which cell towers and sectors the phones connected to when making/receiving calls, sending texts, or using data.
- The records indicated the phones traveled from Philadelphia to Michigan around April 21–23, 2014, and connected to towers in the general areas of the robberies near the relevant times.
- The government sought to offer expert testimony from Christopher Hess to explain how phones connect to towers, how sectoring can narrow a general area, and how historical connections can be used to infer approximate routes.
- A defendant challenged portions of Hess’s methodology, including a proposed “granulization” approach that purported to narrow location more precisely through overlapping sector coverage.

## Issues

1. Whether obtaining historical CSLI from third-party providers under 18 U.S.C. § 2703(d) (rather than a probable-cause warrant) violated the Fourth Amendment, requiring suppression.
2. Whether proposed expert testimony interpreting historical CSLI was admissible under Federal Rule of Evidence 702 and Daubert, and whether portions should be excluded under Rule 403 as misleading or overstated.

## Decision

- The court denied the motion to suppress CSLI.
- The court held that, under then-controlling precedent, defendants lacked a reasonable expectation of privacy in historical CSLI maintained by third-party providers and that a § 2703(d) order was constitutionally sufficient.
- The court granted in part and denied in part the motion to exclude expert testimony.
- The court permitted expert testimony explaining how historical CSLI can place a phone within a tower/sector’s general coverage area and describe limitations affecting tower selection.
- The court excluded or sharply limited testimony suggesting CSLI could pinpoint a phone’s location through “granulization” or other methods implying near-address-level precision.

## Legal Principles

- Under pre-2018 Fourth Amendment doctrine applied by the court, records generated and maintained by third-party service providers may fall within the third-party doctrine such that users lack a reasonable expectation of privacy in the records.
- The Stored Communications Act permits compelled disclosure of certain telecommunications records via § 2703(d) orders upon “specific and articulable facts” showing reasonable grounds of relevance and materiality to an ongoing investigation; the statute does not require probable cause.
- Under Rule 702 and Daubert, expert testimony must be based on reliable principles and methods and reliably applied; courts may assess testing, peer review, error rates, and general acceptance.
- Under Rule 403, courts may limit technical evidence that risks misleading the jury by conveying a false sense of scientific certainty or overstating the precision of an inference from CSLI.

## Conclusion

The court allowed the government to use historical CSLI obtained through a § 2703(d) order and permitted expert testimony describing CSLI’s ability to place a phone in a general tower/sector area, while barring over-precise “granulization” opinions that could mislead jurors about the technology’s locational accuracy.


United States v. Pembrook, 119 F. Supp. 3d 577 (E.D. Mich. 2015)