1001 Smart Cities
🇺🇸 Chicago

ShotSpotter Acoustic Gunshot Detection

🤖 AI-generated summary · ◆ 13 sourced claims · 🔎 Last verified

This overview was generated with AI from the public sources listed below and checked against them before publication. It has not had a complete human fact-check — treat it as a starting point and follow the sources.

13 sourced claims on this page, none individually verified yet — turn on “Sources in the text” to see each one.

How this atlas is made · What “last verified” means · What “source-checked” means · The full record behind this page

✎ Updated 23 Aug 2026 2 sources added. What changed →

The sensors heard the shots. What the city's own inspector general found was that 9.1% of police responses to an alert turned up evidence of a gun crime; the contract lapsed and CPD switched the system off in September 2024.

Outcome🪦 Failed
Evidence📊 Independent
what does this mean?The strongest source is an independent non-academic evaluation: an audit office, a government or EU review, or an NGO. It grades who did the looking — not how well the project went. All four grades →
Run byChicago Police Department, with SoundThinking (formerly ShotSpotter, Inc.)
Scale🏙️ City-wide
Cost≈$53M total contract value (initially $33M for 2018-2021)
FundingCity of Chicago (Chicago Police Department budget)

Part of 1001 Smart Cities — 1,167 documented projects · 🏙️ 7 more in Chicago · 🛡️ Safety & security guide · 📡 Data & IoT projects

Chicago ran ShotSpotter acoustic sensors across 12 of its 22 police districts, more than 100 square miles of the South and West Sides. The city's Inspector General found in 2021 that 9.1% of police responses to alerts turned up evidence of a gun crime. Mayor Brandon Johnson let the contract lapse; CPD stopped using the system on 23 September 2024. No replacement has been procured since.

Completed 📅 2012–2024

📊 Impact

The Chicago Office of Inspector General reviewed every alert confirmed as a probable gunshot and dispatched between 1 January 2020 and 31 May 2021: of those 50,176 alerts, 41,830 recorded a disposition, and 4,556 of those found evidence of a gun-related offence — 9.1% of police responses. A documented investigatory stop followed 2.1%. A synthetic-control evaluation of Chicago and Kansas City funded by the National Institute of Justice found that the software detected gunfire as advertised, but that gun violence did not fall in either city after ShotSpotter arrived and shootings were no more likely to be solved.

🎓 Lesson

Accuracy was never the question Chicago could not answer. The city could hear the shots; what its own watchdog could not find was what the police response produced.

📡 Data & IoTSafety & securitySensors & IoT

Sources

↗ Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021) archived copyThe load-bearing document. Verbatim: 'A total of 50,176 ShotSpotter alerts were confirmed as probable gunshots'; 'a total of 4,556 indicate that evidence of a gun-related criminal offense was found, representing 9.1% of CPD responses'; 'at least one investigatory stop is documented under a matching event number in 2.1% of all CPD responses.' Also dates the contract: '$33 million, three-year contract with ShotSpotter began on August 20, 2018', extended in December 2020 to 19 August 2023. The OIG states its own data were incomplete and irreconcilable. Caution for a future check: the report PDF did not yield machine-readable text in this review, so these figures are quoted from the OIG's release page rather than the PDF body.
↗ Chicago Office of Inspector General — full report PDF (August 2021)Published August 2021The report itself, for readers who want the methodology. It issues none of the recommendations an audit usually carries and says so: OIG describes the document as a descriptive analysis published to inform the public. 985 KB.
↗ National Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control EvaluationPublished 1 January 2023The independent quantitative evaluation, and the reason the entry does not simply repeat advocacy figures. Chicago sample: 85,572 incidents, 6 February 2017 to the end of 2019. Note for anyone reusing it: the frequently quoted procedural gains — alerts arriving 93 seconds before 911 calls, locations about 300 feet closer — are the KANSAS CITY results in this study and are not Chicago findings.
↗ Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)Plain-language account of the same evaluation by its lead author, Eric Piza. Carrying sentence: 'Gun violence did not reduce in either (Kansas City or Chicago) following the introduction of ShotSpotter, and shootings were not anymore likely to be solved in either city.' Piza's own site states the project also produced peer-reviewed journal articles; those were not individually verified here, which is why this entry is graded independent rather than peer-reviewed.
↗ MacArthur Justice Center (Northwestern Pritzker School of Law) — ShotSpotter Generated Over 40,000 Dead-End Police Deployments in Chicago in 21 Months (May 2021)Published 3 May 2021Litigation-side research, published three months before the OIG audit and reaching a similar shape from different data: 1 July 2019 to 14 April 2021, 89% of deployments turned up no gun-related crime and 86% no crime report at all. Labelled here as advocacy research, not an audit — the entry's headline figure is the OIG's, not this one.
Show 8 more sourcesShow fewer
↗ SoundThinking — the vendor's rebuttals to the OIG audit and to the MacArthur Justice Center reportPublished 20 May 2024The other side, kept in deliberately. SoundThinking argues the OIG measured the wrong thing (dispositions of police responses rather than detection accuracy) and published a separate point-by-point response to the MJC study at soundthinking.com/blog/soundthinkings-response-to-the-macarthur-justice-center-report/, plus a commissioned Edgeworth Economics critique of its methodology. The company also renamed itself from ShotSpotter, Inc. on 10 April 2023; the product kept the old name.
↗ ABC7 Chicago — Chicago ShotSpotter contract ends Sunday, city to begin dismantling technology Monday (22 Sep 2024)Updated 23 September 2024The end, with the city's own wording: 'Effective Monday, September 23, 2024, at 12:01 am, the Chicago Police Department will no longer be utilizing ShotSpotter technology', followed by a 60-day decommissioning. Mayor Johnson's stated reason: 'The ultimate goal is to deploy resources on the most effective strategies and tactics proven to accelerate the current downward trend in violent crime. We have to explore better options that save more lives.' The city's own statement page (chicago.gov, February 2024) carries the same text but returns 403 to automated fetching.
↗ WTTW — City Council Votes 33-14 to Again Rebuke Mayor Brandon Johnson's Decision to Scrap ShotSpotter (18 Sep 2024)The fight over the ending, which is not settled. The council voted 33-14 to hand contracting authority to Superintendent Larry Snelling, who supports the technology; Johnson called the ordinance illegal, Snelling did not sign over the objection of the mayor who appointed him, and the system went dark four days later.
↗ Chicago Sun-Times — City Council members want Johnson to tackle replacing ShotSpotter (12 May 2026)Currency check, and the reason this entry says nothing has replaced it. Twenty months after shutdown: 15 firms answered an RFI, 9 answered the RFP including SoundThinking, $13.9M sits in two budgets, no contract is awarded. Chief Procurement Officer Sharla Roberts: 'An RFP of this size, complexity and nature takes 18 to 24 months and sometimes longer to award.' A resolution filed 5 May 2026 with 35 council signatures accuses the mayor of obstruction; hearing set for 3 June 2026. A free six-month muzzle-flash pilot from Shooter Detection Systems was offered in the 9th District in January 2025; no source confirms it went live.
↗ Chicago Sun-Times — Chicago settles ShotSpotter lawsuit, considers bringing gunshot-detection system back (15 Aug 2025)The legal counterpart to the OIG's finding that the technology changed police behaviour: Chicago paid $90,000 to settle a 2022 federal suit by Daniel Ortiz and Derick Scruggs and conceded that a ShotSpotter alert alone does not justify stopping or frisking someone near the alert. Separately, the city agreed in March 2026 to pay $500,000 to Michael Williams, charged with murder in 2020 largely on an alert and held nearly a year before prosecutors dropped the case in July 2021 for lack of evidence.
↗ WTTW — Steep Drop in Homicides Continued for Full Year After ShotSpotter Was Removed: Analysis (29 Dec 2025)What happened after, reported here as correlation and nothing more. Police beats that had had sensors saw roughly a 32% fall in homicides between 1 January and 22 September 2025, but homicides fell about 30% citywide in 2025 to a 60-year low, including where sensors never existed. A University of Chicago analysis reported on 27 May 2026 found faster responses to top-priority 911 calls in former ShotSpotter beats, but it excluded gunfire calls from the data — a limitation critics reasonably press. Both WTTW pages return 403 to automated fetching; figures here come from search-result text and should be re-read before any figure is added to the entry body.
↗ Community Commission for Public Safety and Accountability (City of Chicago) — AboutSupplies the denominator the entry needs and the Inspector General never gives: the ordinance created "a citywide Community Commission and 22 elected District Councils, one in each police district".
↗ South Side Weekly — Which Wards Have ShotSpotter?Published 4 April 2024Ward-level mapping of the sensor network from city records, and the source for the South and West Sides framing: the contract "requires ShotSpotter to monitor twelve police districts on the South and West Sides". It also names the one qualification — free monitoring around Kennedy Expressway billboards on the Northwest Side.

📅 How old is the evidence?

Two clocks, kept apart: when this entry’s sources were published, and what has happened to its record in the atlas. Documented span: 2012–2024. 12 of 13 sources carry a publication date, from 3 May 2021 to 12 May 2026.

When the sources were published

  1. MacArthur Justice Center · ngoMacArthur Justice Center (Northwestern Pritzker School of Law) — ShotSpotter Generated Over 40,000 Dead-End Police Deployments in Chicago in 21 Months (May 2021)
  2. Chicago Office of Inspector General · oversight bodyChicago Office of Inspector General — full report PDF (August 2021)
  3. Chicago Office of Inspector General · oversight bodyChicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021)
  4. National Institute of Justice (NIJ) · national governmentNational Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control Evaluation
  5. South Side Weekly · pressSouth Side Weekly — Which Wards Have ShotSpotter?
  6. SoundThinking · vendorSoundThinking — the vendor's rebuttals to the OIG audit and to the MacArthur Justice Center report
  7. Northeastern University · researchNortheastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)
  8. WTTW News · pressWTTW — City Council Votes 33-14 to Again Rebuke Mayor Brandon Johnson's Decision to Scrap ShotSpotter (18 Sep 2024)
Show 4 more dated sourcesShow fewer
  1. ABC7 Chicago (WLS-TV) · pressABC7 Chicago — Chicago ShotSpotter contract ends Sunday, city to begin dismantling technology Monday (22 Sep 2024) · updated 23 September 2024
  2. Chicago Sun-Times · pressChicago Sun-Times — Chicago settles ShotSpotter lawsuit, considers bringing gunshot-detection system back (15 Aug 2025)
  3. WTTW News · pressWTTW — Steep Drop in Homicides Continued for Full Year After ShotSpotter Was Removed: Analysis (29 Dec 2025)
  4. Chicago Sun-Times · pressChicago Sun-Times — City Council members want Johnson to tackle replacing ShotSpotter (12 May 2026)

Every source, with links ↑

What happened to this record

  1. Sources last read
  2. Entered the record
  3. 2 sources added

Every revision, permanent →

Show your work What this page rests on and what it can’t tell you · all 13 claims with their sources · the forensic record

Evidence Passport · public beta 13 addressable claims, 13 source dossiers, one permanent baseline. The passport is unreviewed — an AI-assisted structural migration, not a human or expert endorsement. Every revision keeps a permanent copy under revision history.

Inspect the claims, one by one — verbatim text, sources and caveats for all 13

The text below is copied verbatim from the published record. Each claim names the source dossiers that carry it; caveats stay attached to the claim they qualify.

Claim 1 clm-dff74cecb61a9a5b quantitative
Chicago ran ShotSpotter acoustic sensors across 12 of its 22 police districts
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The Inspector General's report gives the numerator and the extent: "network coverage in 12 police Districts over 100 square miles". It nowhere states how many police districts Chicago has; the city's own Community Commission page supplies that: the ordinance created "a citywide Community Commission and 22 elected District Councils, one in each police district".
Caveat
The report documents the twelve covered districts by number. It does not state how many police districts Chicago has in total, so the denominator of twenty-two rests on the city's police-district structure rather than on this report.

Sources carrying this claim

  1. Chicago Office of Inspector General — full report PDF (August 2021)
  2. Community Commission for Public Safety and Accountability (City of Chicago) — About
Claim 2 clm-94ca4a36d8e328e9 quantitative
more than 100 square miles of the South and West Sides
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The Inspector General carries the extent verbatim — "over 100 square miles" — but never describes where the coverage lies. South Side Weekly does, from city records: the contract "requires ShotSpotter to monitor twelve police districts on the South and West Sides".
Caveat
South Side Weekly adds the one qualification to a pure South-and-West framing: the vendor also monitored the area around Kennedy Expressway billboards on the Northwest Side, at no charge.

Sources carrying this claim

  1. Chicago Office of Inspector General — full report PDF (August 2021)
  2. South Side Weekly — Which Wards Have ShotSpotter?
Claim 3 clm-ba53ccdbd9c99952 quantitative
The city's Inspector General found in 2021 that 9.1% of police responses to alerts turned up evidence of a gun crime
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The Office of Inspector General published this finding on 24 August 2021: "A total of 4,556 of those 41,830 dispositions indicate that evidence of a gun-related criminal offense was found, representing 9.1% of CPD responses to ShotSpotter alerts." The figure counts what police recorded after responding; it is not a measure of whether the sensors correctly detected gunfire.
Caveat
The figure measures what police documented after responding, not whether a gunshot occurred. The vendor makes exactly this objection, arguing the audit examined the police response rather than the detection.

Sources carrying this claim

  1. Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021)
  2. Chicago Office of Inspector General — full report PDF (August 2021)
Claim 4 clm-501a681c001dd095 descriptive
Mayor Brandon Johnson let the contract lapse
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
WTTW reports the City Council voting 33-14 on 18 September 2024 "to again endorse an effort to overturn Mayor Brandon Johnson's decision to scrap the city's gunshot detection system, ShotSpotter, which is set to be turned off Sunday," and the ordinance sought to move the decision out of the mayor's hands; ABC7 reports that the contract then ended without renewal. WTTW blocks automated retrieval, so its wording was confirmed through search results rather than by opening the page.
Caveat
The ending was contested rather than quiet. The City Council voted twice to reverse the decision and moved to hand the choice to the police superintendent; the system went dark anyway.

Sources carrying this claim

  1. WTTW — City Council Votes 33-14 to Again Rebuke Mayor Brandon Johnson's Decision to Scrap ShotSpotter (18 Sep 2024)
  2. ABC7 Chicago — Chicago ShotSpotter contract ends Sunday, city to begin dismantling technology Monday (22 Sep 2024)
Claim 5 clm-b123ef6c84bc8643 quantitative
CPD stopped using the system on 23 September 2024
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
ABC7 quotes the city's own notice: "Effective Monday, September 23, 2024, at 12:01 am, the Chicago Police Department will no longer be utilizing ShotSpotter technology."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. ABC7 Chicago — Chicago ShotSpotter contract ends Sunday, city to begin dismantling technology Monday (22 Sep 2024)
Claim 6 clm-1206712bac494b17 descriptive
No replacement has been procured since.
Published field
snippet · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
Twenty months after the shutdown the Sun-Times reports that no contract has been awarded: "Nothing has happened since then — even though the last two city budgets set aside a combined $13.9 million for the replacement technology." Fifteen firms answered the request for information and nine answered the request for proposals; Chief Procurement Officer Sharla Roberts said "An RFP of this size, complexity and nature takes 18 to 24 months and sometimes longer to award."
Caveat
A procurement is under way rather than abandoned: nine firms have bid and money is budgeted. What has not happened is an award.

Sources carrying this claim

  1. Chicago Sun-Times — City Council members want Johnson to tackle replacing ShotSpotter (12 May 2026)
Claim 7 clm-8760bdfe792063bf quantitative
The Chicago Office of Inspector General reviewed every alert confirmed as a probable gunshot and dispatched between 1 January 2020 and 31 May 2021: of those 50,176 alerts, 41,830 recorded a disposition, and 4,556 of those found evidence of a gun-related offence — 9.1% of police responses.
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The OIG analysed "all ShotSpotter alert notifications that occurred between January 1, 2020, and May 31, 2021" and reported: "Of the 50,176 confirmed and dispatched ShotSpotter alerts, 41,830 report a disposition — the outcome of the police response to an incident. A total of 4,556 of those 41,830 dispositions indicate that evidence of a gun-related criminal offense was found, representing 9.1% of CPD responses to ShotSpotter alerts." The remaining 8,346 alerts (16.6%) carried no disposition code at all.
Caveat
The 9.1% is calculated against all 50,176 responses, not against the 41,830 that recorded an outcome. For 8,346 alerts no outcome was recorded at all, which the audit treats as a gap in police record-keeping rather than as a finding about the alerts.

Sources carrying this claim

  1. Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021)
  2. Chicago Office of Inspector General — full report PDF (August 2021)
Claim 8 clm-818faf4c0622cc58 quantitative
A documented investigatory stop followed 2.1%.
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The OIG found 1,056 alerts sharing an event number with an investigatory stop report: "at least one investigatory stop is documented under a matching event number in 2.1% of all CPD responses to ShotSpotter alerts." A separate keyword search turned up a further 1,366 stop reports mentioning ShotSpotter whose event numbers matched no alert.
Caveat
The audit says this figure may understate what happened: stops recorded without a matching event number would not appear, and the OIG concluded that police record-keeping was obstructing a meaningful analysis.

Sources carrying this claim

  1. Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021)
  2. Chicago Office of Inspector General — full report PDF (August 2021)
Claim 9 clm-f9aa43c4c940d069 descriptive
A synthetic-control evaluation of Chicago and Kansas City funded by the National Institute of Justice found that the software detected gunfire as advertised
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The National Institute of Justice published the evaluation (award 2019-R2-CX-0004, Piza et al., 1 January 2023), whose Chicago sample is 85,572 gunfire incidents detected between 6 February 2017 and 31 December 2019. Its lead author summarised the detection result as: "All of that I take to communicate that the software does what the vendor promises."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. National Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control Evaluation
  2. Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)
Claim 10 clm-f7a4f9982738ec75 descriptive
gun violence did not fall in either city after ShotSpotter arrived and shootings were no more likely to be solved
Published field
impact · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The evaluation's lead author, Eric Piza, states it plainly: "Gun violence did not reduce in either (Kansas City or Chicago) following the introduction of ShotSpotter, and shootings were not anymore likely to be solved in either city following the introduction of ShotSpotter."
Caveat
The frequently quoted procedural gains from the same study — alerts arriving 93 seconds before 911 calls and locating shootings some 300 feet closer — are the Kansas City results, not Chicago's.

Sources carrying this claim

  1. Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)
  2. National Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control Evaluation
Claim 11 clm-299cb56d5f5f530a descriptive
Accuracy was never the question Chicago could not answer.
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
Both sides of the argument agree on this point. The evaluation's lead author says "the software does what the vendor promises," and the vendor's own rebuttal insists the audit was aimed elsewhere: "it was an audit of CPD's use of the tool, not the efficacy of the tool itself."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. SoundThinking — the vendor's rebuttals to the OIG audit and to the MacArthur Justice Center report
  2. Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)
Claim 12 clm-c07f24b66ce73902 descriptive
The city could hear the shots
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The independent evaluation found the detection worked: its Chicago component logged 85,572 detected gunfire incidents, and its lead author concluded that "the software does what the vendor promises."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024)
  2. National Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control Evaluation
Claim 13 clm-268e2543fef0fd47 descriptive
what its own watchdog could not find was what the police response produced.
Published field
lesson · verbatim
Mapping
mapped · no interpretation or interpolation added by this passport
What the mapping says
The city's Inspector General set out to describe the outcomes of police responses and found it could not: 8,346 of the 50,176 alerts carried no disposition code at all, and the report concludes that if the low stop figure is "attributable in part to missing or non-matched records of investigatory stops... CPD's record-keeping practices are obstructing a meaningful analysis of the effectiveness of the technology."
Caveat
No claim-specific caveat recorded

Sources carrying this claim

  1. Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021)
  2. Chicago Office of Inspector General — full report PDF (August 2021)
Forensic record — source dossiers, gaps, hashes and the exact revision this page renders

This layer records what is known about each source, what is still missing, and the exact snapshot this page is rendering. A missing date, archive or hash stays visible as missing.

unreviewed Revision 2026-08-23-full-claim-array effective 2026-07-26 · created 2026-08-23

Awaiting operator and domain-expert review; publication of this revision implies neither.

sha256:b15d95afae2d640cda6adedc8610fac2bd1db3ba633aebfbdc6a9ce7b392ce2c
Revision history → Permanent version link → Machine-readable record → Evidence Constitution →
13
of 13 claims mapped
13
source dossiers
11
publication dates recorded
1
archives linked
0
exact locators
0
content captures hashed

Governance facts carried by the record

Operator
Chicago Police Department, with SoundThinking (formerly ShotSpotter, Inc.)
Actor types
city-government, private
Funding model
public
Funding description
City of Chicago (Chicago Police Department budget)
Cost
≈$53M total contract value (initially $33M for 2018-2021)
Ownership
Not recorded
Decision rights
Not recorded
Exit conditions
Not recorded

13 source dossiers

Chicago Office of Inspector General — The Chicago Police Department's Use of ShotSpotter Technology (24 Aug 2021) igchicago.org · 4 linked claims

Open original source ↗

Stable source ID
src-f9592ff4f373e5c1
Publisher
Name not classified · igchicago.org
Type / language
web-page · language not classified
Published
2021-08-24
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
Open archived copy ↗ · 2026-06-28
Content hash
No captured content hash
Locator
Open the recorded source note

The load-bearing document. Verbatim: 'A total of 50,176 ShotSpotter alerts were confirmed as probable gunshots'; 'a total of 4,556 indicate that evidence of a gun-related criminal offense was found, representing 9.1% of CPD responses'; 'at least one investigatory stop is documented under a matching event number in 2.1% of all CPD responses.' Also dates the contract: '$33 million, three-year contract with ShotSpotter began on August 20, 2018', extended in December 2020 to 19 August 2023. The OIG states its own data were incomplete and irreconcilable. Caution for a future check: the report PDF did not yield machine-readable text in this review, so these figures are quoted from the OIG's release page rather than the PDF body.

Descriptive only — not page/paragraph exact
Claims linked
Chicago Office of Inspector General — full report PDF (August 2021) igchicago.org · 6 linked claims

Open original source ↗

Stable source ID
src-7fc294f6449adc69
Publisher
Name not classified · igchicago.org
Type / language
pdf · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The report itself, for readers who want the methodology. It issues none of the recommendations an audit usually carries and says so: OIG describes the document as a descriptive analysis published to inform the public. 985 KB.

Descriptive only — not page/paragraph exact
Claims linked
National Institute of Justice — Piza et al., The Impact of Gunshot Detection Technology on Gun Violence in Kansas City and Chicago: A Multi-Pronged Synthetic Control Evaluation nij.ojp.gov · 3 linked claims

Open original source ↗

Stable source ID
src-e94b7add9160654d
Publisher
Name not classified · nij.ojp.gov
Type / language
web-page · language not classified
Published
2023-01-01
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

The independent quantitative evaluation, and the reason the entry does not simply repeat advocacy figures. Chicago sample: 85,572 incidents, 6 February 2017 to the end of 2019. Note for anyone reusing it: the frequently quoted procedural gains — alerts arriving 93 seconds before 911 calls, locations about 300 feet closer — are the KANSAS CITY results in this study and are not Chicago findings.

Descriptive only — not page/paragraph exact
Claims linked
Northeastern University — ShotSpotter improves detection and response to gunfire, but doesn't reduce crime (23 May 2024) news.northeastern.edu · 4 linked claims

Open original source ↗

Stable source ID
src-9b9f7c3c262b943a
Publisher
Name not classified · news.northeastern.edu
Type / language
web-page · language not classified
Published
2024-05-23
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Plain-language account of the same evaluation by its lead author, Eric Piza. Carrying sentence: 'Gun violence did not reduce in either (Kansas City or Chicago) following the introduction of ShotSpotter, and shootings were not anymore likely to be solved in either city.' Piza's own site states the project also produced peer-reviewed journal articles; those were not individually verified here, which is why this entry is graded independent rather than peer-reviewed.

Descriptive only — not page/paragraph exact
Claims linked
MacArthur Justice Center (Northwestern Pritzker School of Law) — ShotSpotter Generated Over 40,000 Dead-End Police Deployments in Chicago in 21 Months (May 2021) macarthurjustice.org · background

Open original source ↗

Stable source ID
src-7db747a75d032fca
Publisher
Name not classified · macarthurjustice.org
Type / language
web-page · language not classified
Published
2021-05-03
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
Open the recorded source note

Litigation-side research, published three months before the OIG audit and reaching a similar shape from different data: 1 July 2019 to 14 April 2021, 89% of deployments turned up no gun-related crime and 86% no crime report at all. Labelled here as advocacy research, not an audit — the entry's headline figure is the OIG's, not this one.

Descriptive only — not page/paragraph exact
Claims linked
Background source; no baseline claim points here
SoundThinking — the vendor's rebuttals to the OIG audit and to the MacArthur Justice Center report soundthinking.com · 1 linked claim

Open original source ↗

Stable source ID
src-8ba47d02a55337b7
Publisher
Name not classified · soundthinking.com
Type / language
web-page · language not classified
Published
2024-05-20
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
Archive
No archived copy linked
Content hash
No captured content hash
Locator
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The other side, kept in deliberately. SoundThinking argues the OIG measured the wrong thing (dispositions of police responses rather than detection accuracy) and published a separate point-by-point response to the MJC study at soundthinking.com/blog/soundthinkings-response-to-the-macarthur-justice-center-report/, plus a commissioned Edgeworth Economics critique of its methodology. The company also renamed itself from ShotSpotter, Inc. on 10 April 2023; the product kept the old name.

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Claims linked
ABC7 Chicago — Chicago ShotSpotter contract ends Sunday, city to begin dismantling technology Monday (22 Sep 2024) abc7chicago.com · 2 linked claims

Open original source ↗

Stable source ID
src-b38a7b4c822f7d07
Publisher
Name not classified · abc7chicago.com
Type / language
web-page · language not classified
Published
2024-09-22
Updated
2024-09-23
Source last checked
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Record last verified
2026-07-26
Dossier created
2026-08-23
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The end, with the city's own wording: 'Effective Monday, September 23, 2024, at 12:01 am, the Chicago Police Department will no longer be utilizing ShotSpotter technology', followed by a 60-day decommissioning. Mayor Johnson's stated reason: 'The ultimate goal is to deploy resources on the most effective strategies and tactics proven to accelerate the current downward trend in violent crime. We have to explore better options that save more lives.' The city's own statement page (chicago.gov, February 2024) carries the same text but returns 403 to automated fetching.

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WTTW — City Council Votes 33-14 to Again Rebuke Mayor Brandon Johnson's Decision to Scrap ShotSpotter (18 Sep 2024) news.wttw.com · 1 linked claim

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Stable source ID
src-479b9a00a9a0d488
Publisher
Name not classified · news.wttw.com
Type / language
web-page · language not classified
Published
2024-09-18
Updated
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Record last verified
2026-07-26
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2026-08-23
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The fight over the ending, which is not settled. The council voted 33-14 to hand contracting authority to Superintendent Larry Snelling, who supports the technology; Johnson called the ordinance illegal, Snelling did not sign over the objection of the mayor who appointed him, and the system went dark four days later.

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Chicago Sun-Times — City Council members want Johnson to tackle replacing ShotSpotter (12 May 2026) chicago.suntimes.com · 1 linked claim

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Stable source ID
src-ccab8aa1e59c6d22
Publisher
Name not classified · chicago.suntimes.com
Type / language
web-page · language not classified
Published
2026-05-12
Updated
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Record last verified
2026-07-26
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2026-08-23
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Currency check, and the reason this entry says nothing has replaced it. Twenty months after shutdown: 15 firms answered an RFI, 9 answered the RFP including SoundThinking, $13.9M sits in two budgets, no contract is awarded. Chief Procurement Officer Sharla Roberts: 'An RFP of this size, complexity and nature takes 18 to 24 months and sometimes longer to award.' A resolution filed 5 May 2026 with 35 council signatures accuses the mayor of obstruction; hearing set for 3 June 2026. A free six-month muzzle-flash pilot from Shooter Detection Systems was offered in the 9th District in January 2025; no source confirms it went live.

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Claims linked
Chicago Sun-Times — Chicago settles ShotSpotter lawsuit, considers bringing gunshot-detection system back (15 Aug 2025) chicago.suntimes.com · background

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Stable source ID
src-621c399c0cd79bdd
Publisher
Name not classified · chicago.suntimes.com
Type / language
web-page · language not classified
Published
2025-08-15
Updated
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2026-07-26
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2026-08-23
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The legal counterpart to the OIG's finding that the technology changed police behaviour: Chicago paid $90,000 to settle a 2022 federal suit by Daniel Ortiz and Derick Scruggs and conceded that a ShotSpotter alert alone does not justify stopping or frisking someone near the alert. Separately, the city agreed in March 2026 to pay $500,000 to Michael Williams, charged with murder in 2020 largely on an alert and held nearly a year before prosecutors dropped the case in July 2021 for lack of evidence.

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Background source; no baseline claim points here
WTTW — Steep Drop in Homicides Continued for Full Year After ShotSpotter Was Removed: Analysis (29 Dec 2025) news.wttw.com · background

Open original source ↗

Stable source ID
src-8667325e3c20090c
Publisher
Name not classified · news.wttw.com
Type / language
web-page · language not classified
Published
2025-12-29
Updated
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Record last verified
2026-07-26
Dossier created
2026-08-23
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What happened after, reported here as correlation and nothing more. Police beats that had had sensors saw roughly a 32% fall in homicides between 1 January and 22 September 2025, but homicides fell about 30% citywide in 2025 to a 60-year low, including where sensors never existed. A University of Chicago analysis reported on 27 May 2026 found faster responses to top-priority 911 calls in former ShotSpotter beats, but it excluded gunfire calls from the data — a limitation critics reasonably press. Both WTTW pages return 403 to automated fetching; figures here come from search-result text and should be re-read before any figure is added to the entry body.

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Background source; no baseline claim points here
Community Commission for Public Safety and Accountability (City of Chicago) — About ccpsa.chicago.gov · 1 linked claim

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Stable source ID
src-20418827a8422f57
Publisher
Name not classified · ccpsa.chicago.gov
Type / language
web-page · language not classified
Published
Not recorded
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
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Supplies the denominator the entry needs and the Inspector General never gives: the ordinance created "a citywide Community Commission and 22 elected District Councils, one in each police district".

Descriptive only — not page/paragraph exact
Claims linked
South Side Weekly — Which Wards Have ShotSpotter? southsideweekly.com · 1 linked claim

Open original source ↗

Stable source ID
src-512cb0d291ba200a
Publisher
Name not classified · southsideweekly.com
Type / language
web-page · language not classified
Published
2024-04-04
Updated
Not recorded
Source last checked
No source-level check date
Record last verified
2026-07-26
Dossier created
2026-08-23
Retrieved copy
No local capture recorded
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Ward-level mapping of the sensor network from city records, and the source for the South and West Sides framing: the contract "requires ShotSpotter to monitor twelve police districts on the South and West Sides". It also names the one qualification — free monitoring around Kennedy Expressway billboards on the Northwest Side.

Descriptive only — not page/paragraph exact
Claims linked
Known limits of this passport
  • Publisher names and source languages have not yet been classified; domains are recorded without guessing.
  • Existing source notes are descriptive locators, not page- or paragraph-exact citations.
  • A missing archive, publication date or content hash is shown as null rather than inferred.
  • The project-level evidence grade ranks the strongest source in the entry; it is not a truth score for every claim.

Continue exploring

Compare this project

🇺🇸 Surveillance Technology Ordinance & Facial Recognition Ban · San Francisco San Francisco requires a published impact report and a Board vote before a department may acquire a technology like this. 🇺🇸 Operation LASER & PredPol — Predictive Policing · Los Angeles Both ended after their own inspector general looked: LA could measure no crime effect; Chicago found evidence in 9.1% of responses. 🇺🇸 Array of Things · Chicago Chicago's other sensor network, same years: the Array published air and noise readings openly; these microphones fed police dispatch.

The same sensors, and the audit that decided their fate

Two cities bought the same acoustic gunshot-detection system and inherited the same criticisms. Only one of them commissioned the study that could settle the argument — and that, not the hardware, decided what happened next.

ProjectSinceStatusOutcomeEvidenceRun byCostWhat settled it
ShotSpotter Acoustic Gunshot DetectionChicago, 🇺🇸 2012 Completed Failed Independent City government, Private company ≈$53M total contract value (initially $33M for 2018-2021) The city's own Inspector General reviewed it, the contract was allowed to lapse, and police stopped using the system in September 2024.
ShotSpotter Acoustic Gunshot Detection, In Service Since 2006Washington D.C., 🇺🇸 2006 Live Ongoing Media City government, Private company At least $5.16M paid to SoundThinking since 2016; no current contract value or term is public The same sensors, running since 2006 and still running: no equivalent review was ever commissioned, so nothing forced a decision.

Explore the wider context

📟 A Reading Is Not a Decision💥 Failed & Instructive📖 Evidence brief📖 Automated speed enforcement (speed cameras)📖 Flood early-warning system
📎 Cite this project

1001 Smart Cities (2026). “ShotSpotter Acoustic Gunshot Detection” — Chicago, United States. The Smart City Atlas. https://1001smartcities.org/projects/chicago-shotspotter/ (last verified 2026-07-26). Data: CC BY 4.0.

The underlying data is free to reuse with attribution — see the open data page.

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