DEASIL License Plate Tracking in Arizona: What It Is, Who Uses It, Constitutional Issues, and How to Protect Yourself
If you’re under investigation or facing charges related to license plate data, call now for a confidential case review.
What is “DEASIL” license plate tracking?
DEASIL (often accessed at a DOJ portal) is the DEA’s interface to the National License Plate Reader Program (NLPRP). In plain English, it’s a federal system that lets authorized agencies query billions of automated license plate reader (ALPR) scans and set real-time alerts (“hot lists”) on plates of interest. The DEA’s own Privacy Impact Assessment explains that NLPRP aggregates federal, state, local, tribal, and certain special-jurisdiction cameras, and authorized partners search it through the DEASIL interface. The database typically includes the plate number, date/time, GPS location, travel direction, and a photo of the vehicle/scene.
Where is DEASIL/ALPR data used?
Interstate corridors & border-adjacent routes. DEA positions LPR cameras along “high-level drug and money trafficking corridors” and connects them to a nationwide network. In Arizona, this often means major highways, such as I-10, I-8, and I-17, as well as other arterial routes commonly used for interdiction.
State & local agencies across Arizona. Public records reporting shows that the Arizona DPS and local departments (e.g., Mesa PD) share and receive ALPR data through vendor networks (such as Vigilant) and other agencies—illustrating how local scans can flow nationally.
Municipal deployments & HOAs. Cities and private communities deploy ALPRs for theft deterrence and investigations; vendors (e.g., Flock, Leonardo/ELSAG, Motorola/Vigilant) market systems that generate alerts and retain searchable history.
Federal investigative use. Congress’ nonpartisan research arm confirms that the DEA administers the NLPRP to facilitate complex investigations; ALPR use is widespread in U.S. policing. DHS also describes ALPRs as a long-standing law enforcement tool.
Who has access?
DEA (primary) and federal partners via the DEASIL interface.
State, local, and tribal law enforcement with authorized access and sharing agreements.
Private vendors (Vigilant/Motorola, Flock, ELSAG/Leonardo) collect and manage large ALPR datasets and may one-way share with law enforcement, depending on contracts and policy.
Policy note: Some jurisdictions have tightened cross-border sharing and retention practices (e.g., recent California guidance limiting out-of-state sharing). Expect patchwork rules and frequent policy changes.
What data is captured?
Plate number and state (OCR-derived)
Date/time, GPS coordinates, roadway/lane, direction of travel
One or more photos of the plate, vehicle, and surroundings
Camera ID/site metadata
Potential Constitutional issues with ALPR/DEASIL use
1) Fourth Amendment of the U.S. Constitution
Two U.S. Supreme Court decisions frame the modern debate:
United States v. Jones (2012): Physically attaching a GPS tracker to a car to monitor movements is a search. While ALPRs aren’t GPS devices, Jones recognized that long-term vehicle tracking raises serious privacy concerns.
Carpenter v. United States (2018): Aggregating historical location data over time (127 days of CSLI) requires a warrant; the Court acknowledged that long-term, comprehensive tracking can invade reasonable expectations of privacy even when data sits with third parties. Many courts and scholars analogize dense ALPR histories to Carpenter’s “mosaic” of movements.
Why it matters in ALPR cases: A single plate scan on a public road usually isn’t a search. However, building a months-long travel profile using networked readers (or querying DEASIL for a vehicle’s history) can resemble Carpenter’s long-term location surveillance, bolstering motions to suppress when police lack a warrant or exceed statutory authority. Keep in mind, courts are still developing the doctrine.
2) Arizona Constitution — Article 2, § 8 (“Private Affairs” Clause)
Arizona’s Constitution provides: “No person shall be disturbed in his private affairs, or his home invaded, without authority of law.” Arizona courts sometimes view this clause as more protective than the Federal Fourth Amendment, depending on context. While recent cases have limited privacy expectations in certain digital records (e.g., IP/ISP subscriber information), the text of § 8 provides experienced defense attorneys with additional ammunition to challenge broad, historical location surveillance assembled from ALPR/DEASIL queries without a warrant.
3) Data sharing & retention risks
Arizona reporting shows wide sharing among agencies; national civil-liberties groups have flagged federal access and large-scale retention as risks for dragnet tracking of ordinary people. Where retention is long and sharing is broad, Carpenter-style arguments become stronger.
Common law enforcement uses in Arizona cases
Travel history of drivers, including innocent civilians
BOLO/Hot-list hits leading to stops or seizures
Back-tracking a suspect vehicle’s route to place a defendant near a crime scene
Identifying associates by cars that repeatedly travel together
Probation/parole monitoring and warrant service
Vendors openly market these capabilities; the DEA and DHS describe ALPRs as integral to investigations.
Can you avoid being tracked by DEASIL/ALPR?
Realistically, you can’t opt out of being seen on public roads. But you can reduce legal exposure:
Keep your plate lawful and unobstructed. Tinted covers, sprays, flips, and plate obstructions can trigger stops and lead to separate charges. (Tampering is illegal and won’t defeat OCR reliably.)
Know the limits of “privacy tech.” Randomizing routes or using car-share services doesn’t remove past scans already in vendor or DEASIL databases.
Challenge the data in court. A defense attorney can:
Demand warrants or legal process authorizing bulk ALPR queries/DEASIL searches.
Attack probable cause and particularity (especially for historical, long-term data collection).
Seek retention, sharing, and audit logs from agencies and vendors (Vigilant/Motorola, Flock, etc.).
Argue Carpenter/Jones “mosaic” theories, and invoke Arizona’s Private Affairs Clause for added protection.
Important: Some states set statutory limits on ALPR retention/sharing; Arizona’s landscape is shaped more by agency policy and general constitutional principles. Local practices evolve—another reason to get an experienced Arizona-specific lawyer on your side.
Common issues we experience with the license plate tracking
One of the most common issues we encounter at Millar Law is the tracking of innocent people. DPS (State Police), along with other agencies, will use license plate tracking as a basis to stop and search a vehicle. Often, these stops result in unconstitutional searches and seizures, violating our client’s constitutional rights. Many of our clients are unaware that the officer used license plate tracking data to establish reasonable suspicion or probable cause of a crime. These issues are typically only discovered once we review the evidence (reports, body camera footage, etc.).
It is crucial to call an experienced criminal attorney if you or someone you know is facing charges, especially if the investigation appears to be unreasonable. We have successfully had evidence suppressed and cases dismissed based on these unconstitutional searches and seizures.
What to do if ALPR/DEASIL data shows up in your case
Call us to speak with an experienced Arizona criminal defense attorney immediately. Early intervention helps preserve discovery and suppression issues.
Preserve evidence. Request that the State and any vendors preserve all ALPR records, hot-list criteria, sharing logs, and retention settings used in your case.
File motions to suppress unconstitutional evidence. Suppression challenges may be appropriate if affidavits mischaracterize ALPR hits or fail to provide the context of retention and sharing.
Cross-examination reliability. OCR errors, camera calibration, and context (such as stolen plates or multiple drivers) are all factors that matter. The DEA PIA itself acknowledges OCR fallibility.
FAQs
Is it legal for police in Arizona to scan every plate?
Generally, yes—a single scan on a public road is typically not a “search.” However, mass, long-term tracking compiled through networks (including DEASIL) raises constitutional questions under Carpenter/Jones and Arizona’s Constitution, specifically under § 8.
Do federal agents need a warrant to pull my plate history from DEASIL?
The Supreme Court hasn’t ruled directly on ALPR history. Many arguments mirror Carpenter (long-term location records often require a warrant). Outcomes depend on facts, scope, and jurisdiction—exactly what we litigate at Millar Law.
Can DEASIL data be wrong?
Yes. OCR misreads and plate cloning occur; context (time, place, vehicle make/color) is crucial.
Who else sees Arizona scans?
Depending on local laws and contracts, DPS/local agencies may share widely and receive data from hundreds of agencies; federal systems like DEASIL aggregate data from many sources.
Talk to an Arizona Defense Attorney Who Knows ALPR/DEASIL
If ALPR or DEASIL evidence is part of your case—or you think you were stopped because of a plate “hit”— Call Millar Law Today. We know how to challenge mass-surveillance evidence, demand audit logs and vendor records, and develop suppression strategies in accordance with both the U.S. Constitution and Arizona’s Constitution.
Call now for a free, confidential consultation.
At Millar Law, we serve clients throughout Phoenix, Maricopa County, and across the state of Arizona.
Key Sources & Further Reading
DEA Privacy Impact Assessment for the NLPRP/DEASIL (system purpose, access, data elements).
CRS (Library of Congress) Report on law-enforcement use of ALPRs and DEA’s administration of NLPRP.
Carpenter v. United States (2018) and United States v. Jones (2012) (location-tracking privacy).
Arizona Constitution, Article 2, § 8 (“Private Affairs” Clause).
This article is for informational purposes and not legal advice. For advice about your situation, call us directly.
