Does it really help with crime?
The federal government's own evidence clearinghouse rates this technology “Ineffective.” Two randomized controlled trials tested it against a control group and neither found a reduction in crime. And the vendor's headline statistic came from a customer survey whose lead researcher now says the underlying police data could not support the analysis.
“Ineffective — more than one study”
“There were no statistically significant program effects on general crime, auto-related crime, vehicle-theft calls for service, or auto-theft.”
What has to be said with it: The page carries a notice that it is no longer being updated, posted May 16, 2013. The rating rests on the two randomized trials below, both of which studied patrol-car-mounted readers rather than the fixed camera networks cities buy today. Cite it as what it is — the federal evidence rating, and an old one.
Source · CrimeSolutions, Office of Justice Programs, U.S. Department of Justice
The two controlled trials
License Plate Recognition Technology: Impact Evaluation and Community Assessment
A two-jurisdiction randomized experiment in Alexandria and Fairfax County, Virginia found no crime reduction.
“the use of LPR in autotheft hot spots does not appear to result in a reduction of crime generally or autotheft specifically, during the period of time measured”
RCT · read it
Limitation: Patrol-car-mounted readers, measured over a limited period. The authors also state the separate point that efficiency gains are undisputed — more plates read — and that this is a different question from whether crime falls.
Combating Vehicle Theft in Arizona: A Randomized Experiment With License Plate Recognition Technology
A randomized trial in Mesa, Arizona placing readers in auto-theft hot spots. More plates read and more stolen vehicles recovered — and no deterrent effect on auto theft compared with control areas.
RCT · read it
Limitation: Patrol-car-mounted readers, one city, 2012.
What the peer-reviewed reviews found
Readers were used in roughly 5–7% of relevant investigations, and clearance occurred in about 19% of the cases where they were used.
“for almost three-quarters of this sample where ALPR use was noted, ALPRs did not contribute in any meaningful way to the resolution of an investigation”
SYSTEMATIC REVIEW · Cynthia Lum, Christopher Koper, YongJei Lee, Daniel Nagin, Lawrence Sherman · read it
Limitation: A review and theoretical piece, not a new impact evaluation. It also reports that 59% of agencies using readers in patrol gave officers complete discretion over how they use them, without specific guidance.
What the vendor says, and where the number came from
"10% of reported crime in the U.S. is solved using Flock technology"
Flock states its technology "helps resolve roughly 700,000 crimes a year … about 10% of reported U.S. crime."
Source · flocksafety.com
What is missing: The figure comes from a survey of Flock's own customers, 123 agencies, April–June 2023. The published page never defines "solved." The researcher who oversaw the study later said the underlying police data were "too varied and incomplete for us to do any type of meaningful statistical analysis on them."
2025 Impact Census
Claims roughly 1 in 5 resolved cases involved Flock technology, and about 10,000 missing persons located per year.
“are intended to show order-of-magnitude impact and should be read as directional estimates rather than audited totals”
Source · flocksafety.com
What is missing: Agencies reported raw counts only if they formally tracked them, and otherwise supplied percentage estimates. Nobody checked the numbers independently.
Flock Installed AI Cameras In This Small City And Claimed Crime Went Down. It Went Up.
In San Marino, California, Flock marketed an 80% drop in residential burglaries. Burglaries were up 5% over the period and total Part 1 crimes were flat.
“I definitely need to talk to their marketing folks.”— San Marino Police Chief John Incontro
JOURNALISM · Cyrus Farivar · read it
Limitation: Journalism, not a study. Flock's response, included in the piece: "We do not claim that because San Marino, California reported an 80% drop in residential burglaries, the city of Los Angeles would see the same."
How many crimes has Flock Safety solved in Cleveland?
Asked how many crimes the readers had solved, Cleveland police and prosecutors could not produce a count.
“police reports, investigative supplements and related case materials are not written or maintained for the purpose of allowing a researcher to later isolate and measure the efficacy of a single investigative tool”— Cleveland Division of Police
JOURNALISM · Olivia Mitchell · read it
Limitation: One city. The point it establishes is about record-keeping, not about effectiveness: the question may not be answerable from case files at all.
And here is the evidence that cuts the other way
Automated License Plate Readers, Vehicle Theft, and Clearance
Across 216 agencies with staggered deployment, an approximately 11% reduction in motor vehicle theft, a roughly 16% increase in motor-vehicle-theft arrests, and stolen vehicles recovered about six hours sooner.
“not all of the increase in clearance can be attributed to the ALPRs themselves”
CrimRxiv working paper · 2026 · read it
Limitation: This is the strongest evidence on the favourable side and it belongs on the page. Two things must be said with it: it has not cleared peer review, and Flock supplied the deployment data the study is built on. The authors themselves concede arrests were already rising before deployment.
The Impacts of Large-Scale License Plate Reader Deployment on Criminal Investigations
Survival analysis of roughly 100 fixed readers in one major U.S. city. Clearances for auto theft and robbery improved after installation, especially where cameras were dense.
“may have the potential to improve investigative outcomes for some serious crimes”
Police Quarterly 22(3) · 2019 · read it
Limitation: The improvements were not statistically significant in multivariate analysis, and the authors note other factors may also have contributed. This is the closest peer-reviewed analogue to a fixed camera network.
An Evaluation of a Major Expansion in ALPR Technology
Fixed readers on all entrances and exits of Atlantic City, New Jersey. The expansion did not reduce violent crime, but was associated with reductions in shootings, motor vehicle thefts, and property crime.
Justice Evaluation Journal · 2025 · read it
Limitation: Interrupted time-series without a control jurisdiction. The publisher's page refused retrieval; this entry rests on an open mirror, and the author list and effect sizes could not be confirmed.
Annual Report — Law Enforcement Use of ALPR
A state body's own summary of the evidence base.
“Most of the information on ALPR successes, errors, and misuses is anecdotal. There is a relatively limited body of research that rigorously evaluates its effectiveness across various public safety outcomes.”
Virginia State Crime Commission · 2024 · read it
Limitation: The same report credits the technology with identifying stolen vehicles and increasing recoveries and related arrests, and calls for more research. It published no hit-rate, alert, or arrest statistics of its own.