Bottom line:
Historical CSLI (cell site location information) records carriers already keep generally requires a warrant under the U.S. Supreme Court’s Carpenter v. United States (2018).
Real-time CSLI (prospective tracking) also requires warrant-level process under Pennsylvania law; the PA Supreme Court’s Commonwealth v. Pacheco (2021) scrutinized “orders” that function like warrants and demanded Carpenter-style protections.
Pennsylvania’s Constitution (Art. I, § 8) can provide more protection than the federal floor—Commonwealth v. Alexander (2020) is the most recent, big example (automobile searches), and its reasoning influences digital-privacy analysis.
A brief history: from pen registers to CSLI
Pen registers & the third-party doctrine (1979–2000s): police often obtained dialed-number records and later basic phone metadata without warrants, relying on the idea that you “shared” it with a company.
The smartphone turn: As carriers began logging connection events to nearby towers, CSLI datasets could reconstruct people’s movements over days or months. In 2018, the Supreme Court held that obtaining historical CSLI is a Fourth Amendment search that generally requires a warrant, stressing the “near perfect surveillance” such records enable.
Why that matters: The warrant rule in Carpenter reshaped how police, providers, and courts treat historical records. It also helped drive Pennsylvania’s approach to real-time tracking.
Pennsylvania’s path on real-time CSLI
Before Carpenter, agencies sometimes used state “tracking” or provider-records orders for prospective pings. Pennsylvania has since aligned warrant requirements across the board:
Commonwealth v. Pacheco (Pa. 2021): The Court evaluated real-time CSLI orders as functional warrants—requiring probable cause, particularity, and Carpenter-level rigor. The Court warned that if the Commonwealth cannot meet those requisites, suppression follows.
Procedural & statutory backdrop:
18 Pa.C.S. § 5743 (provider disclosures) and related Chapter 57 provisions govern when law enforcement can compel carrier records, layered on top of warrant requirements.
210 Pa. Code Rule 3545 lays out what an order must contain for mobile communication tracking (probable cause, identity fields, offenses, and a 60-day cap). Treat this like warrant-level process post-Carpenter/Pacheco.
Exigency still exists, but it’s narrow. Pennsylvania’s Article I, § 8 jurisprudence generally demands both probable cause and exigent circumstances to excuse a warrant in comparable contexts (e.g., vehicles). Courts are cautious about stretching “exigency” to routine phone tracking. Expect suppression where agencies rely on thin emergency rationales instead of getting a warrant.
Historical CSLI after Carpenter
Warrants are the norm. The Supreme Court emphasized how historical logs enable retrospective, comprehensive tracking—so the old “third-party doctrine” isn’t enough by itself.
Pennsylvania courts have followed suit, treating historical CSLI as sensitive data demanding a probable-cause warrant absent a recognized exception.
2025 developments to watch: geofence/keyword “big data” warrants
Although not CSLI per se, geofence warrants (Google “Location History” around a crime scene/time) are the next frontier of location privacy:
In September 2025, the Pennsylvania Superior Court upheld a Google geofence warrant, crediting narrow time and place parameters and multi-step minimization. (Look for the Choice line of decisions; PSP Trooper Tray’s affidavits figured prominently.)
Nationally, the issue is hot and split—some courts approve geofences; others disallow them as overbroad dragnets. Expect spillover arguments into CSLI reasonableness, particularity, and good-faith debates.
Mapping and analysis tools (CellHawk, etc.): what they do—and don’t
Investigators (and defense experts) don’t plot towers by hand anymore. Tools like CellHawk import carrier returns (call-detail/CSLI), then map, timeline, heat-map, and link devices and events across providers. They can also visualize geofence or ride-share/GPS data. None of this replaces legal process—it’s analysis after the data is obtained.
Defense angle: ask for the full ingest → transform → analyze chain (what was fed in; what filters; what assumptions about sector coverage; whether drive-testing validated ranges). Cross-examine heat-maps that imply precision beyond what tower density supports.
Practical guidance
For clients (non-lawyers)
Assume phones are trackable. Keep your device locked; don’t consent to a “quick look.” A warrant is usually required to search contents; location orders must meet Carpenter/Pacheco rigor.
If your phone is seized, ask for a lawyer and avoid providing passcodes/biometrics until counsel advises (separate Fifth-Amendment issues).
For defense counsel
Early preservation & targeted discovery
Demand the warrants/orders, affidavits, returns (historical and real-time), including provider certifications and any emergency-disclosure paperwork. Cite § 5743 and Rule 3545.
Request tool outputs: raw carrier files, parsing logs, CellHawk project files, settings, heat-map parameters, and any validation (drive tests, RF analysis).
Suppression theories (common)
No warrant / wrong process for historical CSLI (Carpenter).
Real-time orders lacking probable cause/particularity (Pacheco).
Overbreadth / lack of minimization in geofences and “reverse” returns (time/place too wide; step-two/three identification too loose). Pennsylvania’s 2025 case shows what courts expect when they uphold them—use it as a ceiling, not a floor.
Good-faith limits: where law was settled locally (e.g., warrants for CSLI), argue exclusion even if officers thought the SCA or a generic “tracking” order was enough.
Expert workups
Hire a radio-frequency/telecom expert to address tower sectorization, handoffs, and coverage. Re-map with alternative parameters to test the prosecution’s story. If CellHawk (or similar) was used, replicate with the same input files and disclose discrepancies.
For prosecutors (what wins on appeal)
Show narrow windows (short time spans), tight geographies, and particularized probable cause.
Use stepwise minimization for geofences; document every narrowing step.
Keep a clean audit trail from provider return to courtroom exhibit; provide certifications and tool provenance.
Quick reference (primary sources)
Historical CSLI requires a warrant: Carpenter v. United States, 585 U.S. 296 (2018) (PDF). (Supreme Court)
Real-time CSLI scrutiny / warrant-equivalents: Commonwealth v. Pacheco (Pa. 2021). (Pennsylvania Courts)
Article I, § 8 can go beyond the federal floor: Commonwealth v. Alexander (Pa. 2020). (Justia Law)
PA provider-disclosure framework: 18 Pa.C.S. § 5743 (and related Chapter 57 sections). (Justia Law)
Order requirements for mobile-tracking process: 210 Pa. Code Rule 3545. (pacodeandbulletin.gov)
Geofence in PA (2025): Superior Court opinions upholding a tightly drawn geofence (see Choice/J-A20010-25, Sept. 18–19, 2025). (Pennsylvania Courts)
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