533 F.Supp.3d 779
N.D. Cal.2021Background
- Defendant Brian Wendt moved to exclude or limit proposed testimony by FBI Special Agent Meredith Sparano of the Cellular Analysis Survey Team (CAST), who analyzed call detail records (CDRs) and prepared illustrative maps using proprietary ESPA mapping software.
- Sparano’s proffered testimony: explanation of how CDRs identify the tower/sector a phone used and that such records establish an approximate (not exact) geographic area; she created a PowerPoint with tower "wedges" and timeline tables; no drive tests were performed in this case.
- Defendants do not dispute CDR accuracy or basic cell-to-tower mechanics but challenge admissibility of the mapping slides and reliance on proprietary ESPA software, arguing Rule 16, Rule 702/Daubert, authentication, Confrontation Clause, and Rule 403 problems.
- The government disclosed Sparano’s declaration, drafts of the slideshow, identified ESPA, described peer-review protocols, and produced all underlying CDRs; court held a hearing and ordered final exhibit disclosures before trial.
- The court found Sparano qualified on historical cell-site analysis, concluded CAST mapping testimony is admissible when limited to general/approximate locations, and denied the motion to exclude or limit her testimony under Rule 702/Daubert and alternative theories, with narrow caveats about overstating precision and one problematic slide.
Issues
| Issue | Plaintiff's Argument (Gov) | Defendant's Argument (Wendt/Ott/Diaz) | Held |
|---|---|---|---|
| Admissibility under Rule 702/Daubert of CAST historical cell-site analysis | Historical cell-site analysis is reliable to show general/approximate phone location; Sparano is qualified and her methodology (as disclosed) meets Daubert; maps are demonstratives and can be independently verified. | Sparano lacks needed expertise in ESPA and radio propagation; her methodology is unreliable without drive tests or consideration of tower/antenna/terrain variables. | Denied. Agent qualified; methodology reliable for showing approximate locations if she does not overstate precision; lack of drive tests goes to weight, not automatic exclusion. |
| Reliance on proprietary ESPA mapping software / need for access | ESPA produced demonstratives; government produced underlying CDRs so maps are verifiable with public tools; expert need not be software engineer. | ESPA is a law-enforcement-only "black box"; defense must have access or expert must understand algorithms to verify outputs. | Denied. ESPA use acceptable because maps can be independently verified from CDRs; requiring software-source access would be impractical and unnecessary. |
| Rule 16(a)(1)(G) disclosure adequacy | Government provided declaration, identified ESPA, explained workflow and peer-review, and produced CDRs and slideshow drafts. | Disclosures insufficient about software and methods; Ninth Circuit precedent (Budziak) requires deeper disclosure when software central. | Denied. Disclosures met Rule 16 and the court’s January 13 order; Budziak inapposite because software here does not bear on an element of the offense. |
| Authentication, Confrontation Clause, and Rule 403 objections to slides | Maps/illustratives are admissible, can be authenticated by Sparano, and underlying CDRs are business records (not testimonial); slides aid juror comprehension. | Maps may be unauthenticated, contain hearsay/testimonial material, and be unfairly prejudicial or misleading (e.g., arrows or statements asserting defendants were "traveling together"). | Authentication & Confrontation Clause: denied—Sparano can authenticate and CDRs fall within business-records framework; not Bullcoming/Melendez-Diaz issue because preparer testifies. Rule 403: generally denied, but court flagged and may exclude/limit specific slides that assert unsupported or misleading inferences (e.g., explicit "traveling together" statement). |
Key Cases Cited
- Daubert v. Merrell Dow Pharm., 509 U.S. 579 (1993) (trial court gatekeeping standard for expert testimony)
- General Electric Co. v. Joiner, 522 U.S. 136 (1997) (appellate review of Daubert admissibility is for abuse of discretion)
- Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999) (Daubert principles apply to all expert testimony, not only "scientific")
- Primiano v. Cook, 598 F.3d 558 (9th Cir. 2010) (reliability and relevance standards for expert testimony)
- Estate of Barabin v. AstenJohnson, Inc., 740 F.3d 457 (9th Cir. 2014) (factors for assessing expert reliability; en banc guidance)
- United States v. Sandoval-Mendoza, 472 F.3d 645 (9th Cir. 2006) (district court’s gatekeeping role)
- United States v. Hill, 818 F.3d 289 (7th Cir. 2016) (historical cell-site analysis admissible to show general location if precision isn’t overstated)
- United States v. Morgan, 292 F. Supp. 3d 475 (D.D.C. 2018) (drive-testing and tools for approximating tower coverage are admissible; experts need not know underlying software algorithms)
- United States v. Alatorre, 222 F.3d 1098 (9th Cir. 2000) (Daubert hearing not always required)
- United States v. Lizarraga-Tirado, 789 F.3d 1107 (9th Cir. 2015) (machine-generated map labels vs. human assertions and authentication considerations)
- United States v. Yeley-Davis, 632 F.3d 673 (10th Cir. 2011) (cell-site records are business records and not testimonial for Confrontation Clause purposes)
- Bullcoming v. New Mexico, 564 U.S. 647 (2011) (Confrontation Clause requires analyst who prepared forensic report be available for cross-examination)
- Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009) (similar confrontation principles for forensic reports)
- United States v. Jones, 918 F. Supp. 2d 1 (D.D.C. 2013) (use of cell records to determine general phone location widely accepted)
- United States v. Medley, 312 F. Supp. 3d 493 (D. Md. 2018) (recognizing environmental and technical factors affect tower coverage area)
- United States v. Evans, 892 F. Supp. 2d 949 (N.D. Ill. 2012) (plotting tower locations on Google Maps does not require specialized technical knowledge)