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Inner-City Crime and the Built Environment:
Evidence-Based PolicyLawrence W. Sherman
Institute of Criminology, Cambridge UniversityJerry Lee Centre of Experimental Criminology
24th February 2014
00.20.40.60.8
11.21.41.6
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Targeting: Hot Spots of Violent Crime, Tokyo
Testing: Residual Deterrent Effects of Police Patrol on Crime in Hot Spots
Maximized by 15 minute periods of patrol presence: The “Koper Curve”
LogTimeToFirstCrimeAfter PoliceLeave
Minutes of Police Visit (n =7,000)
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7000
6pm-8am 6pm-8am 6pm-8am 6pm-8am 8am-6pm 8am-6pm 8am-6pm 8am-6pmA B C D A B C D
Total Patrol Time 5838 2773 3265 4637 4605 6496 5980 3164Total Patrol Geo-fence HS 1362 127 609 388 683 1289 1552 712
Num
ber o
f MIn
utes
Ratio of Patrols in and out HotSpots in MinutesTeam CommandersTeam A) - 12487 A/Sgt. AliTeam B) - 13523 A/Sgt. RichardsonTeam C) - 13849 A/Sgt. TitusTeam D) - 13588 A/Sgt. Paul
Report Period- 12/1/14 to25/1/14
TRACKING
How Does Research Prevent Disease?
THE TRIPLE-T STRATEGY for applying research to solve probems
• Targeting (epidemiology, concentrations)
• Testing (evaluating prevention, response)
• Tracking (surveillance: delivery, outcomes)
T-T-T is generalizable to allpopulation management
• Politics (Obama)• Business customers• Employees • Baseball players (“Moneyball”)• Crimes and criminals• My focus on “evidence-based policing”Sherman, 2013 “The Rise of Evidence-
Based Policing: Targeting, Testing, Tracking” CRIME AND JUSTICE 42
2 Main Targets for Crime Prevention
I. Individual CriminalsKey Dimensions:WhoCurrent ageAge of crime onsetAge of last arrestWhat kinds of crimesFamily Links to co-offendersSeverity of harmVolume of events
II. Criminal IncidentsKey Dimensions:WhatWhere WhenHowWhyN of offendersN of victimsSeverity of harmVolume of events
The Criminology of Places
• Granular Data Revolution—1980s• Within neighbourhoods• Micro-places• Micro-times• Recurrent Situations (“Problems”)• Incentive structure (Cash, portable value)• Scarce resources• Return on investment
I.a. Targeting: Hot Spots of Violent Crime, Tokyo
Pareto Curves: a “Power Few”
Long-Term Patterns, Seattle 14 yrsD. Weisburd et al 2004
Peterborough: 50% of Calls to 1.3% of addresses—8 years
I.B. Testing
General Deterrence Hypothesis: • Effects of concentrating patrols to match• Concentrations of crimes in• Space and Time? “Hydraulic” Displacement Hypothesis:Criminal motivations cause fixed N of crimesEach crime deflected by police patrol willMove to another place and time—no net
effect of focused patrol
First Test of Hot Spots Patrol
• Minneapolis Hot Spots Experiment(L. Sherman & D. Weisburd 1995)
• 110 Hot Spots (Street corners)• 55 got extra patrol—RCT• 18 Observers counted patrol time, crime• 50% fewer Calls for service• 2/3 reduction in robbery• 50% reduction in disorder
ChangeInCrime
-10%
-5%
0%
5%
10%
15%
20%
25%
30%
Total Calls Soft Crime Hard Crime
ControlExp.
Optimal Patrol Time Per Location: 10-15 Minutes
• Minutes policePresent à Minutes to first crime afterPolice leave theHot Spot = “Residual Deterrence”(L. Sherman 1990)
Testing: Residual Deterrent Effects of Police Patrol on Crime in Hot Spots
Maximized by 15 minute periods of patrol presence: The “Koper Curve”(C. Koper, 1995)
LogTimeToFirstCrimeAfter PoliceLeave
Minutes of Police Visit (n =7,000)
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New Dosage Measurement Technology
• GPS locator• 13 second “ping”• Can measure time• In “Geo-fences”• Track what public
sees• Replaces researchstudents with
stopwatches!
Pioneering GPS-Based Hot Spots Experiments
• Lecturer in Evidence-Based Policing
• Former Police Inspector in Israel
• Prize-winner
Dr. Barak Ariel
19,821
22,311
10000
12000
14000
16000
18000
20000
22000
24000
26000
28000
30000
Control Exp't
min
utes
Birmingham: Total Number of Minutes Officers Spent in 41 Treatment Hotspots and 41 Control Hotspots (15
days)
Chart shows reductions in all areas that are patrolled, except for BDH and Making Off W/O Payment.
90D
B. Ariel, A. Hebb, D. Vajzovic :72 Hot Spots in Peterboro (Preliminary findings)
Cont.
150 meter radiusPer hotspot
More than 250 meters between hotspots
Crime Hotspots before RA
165.67
65.60
20.31
166.60
62.78
20.04
- 20.00 40.00 60.00 80.00
100.00 120.00 140.00 160.00 180.00
High Level Hotspots(120+ crimes per
hotspot)
Mid Level Hotspots(25-120 crimes per
hotspot)
Low Level Hotspots(15+ crimes per
hotspot)
mean Pet. (annualised 12 months) Tmean Pet. (annualised 12 months) C
Mean time spent inside hotspots per day by PCSOs
00:16:42
00:09:46
00:05:02
00:44:51 00:43:41
00:29:06
00:00:00
00:07:12
00:14:24
00:21:36
00:28:48
00:36:00
00:43:12
00:50:24
Hot hotspots Medium Hotspots Low Hotspots
ControlExperimental
Distribution of offences first five months by blocks
22022018
1537
1290
25583
0
500
1000
1500
2000
2500
control experimental
Hot hotspots Medium Hotspots Low Hotspots
Mean time spent inside hotspots per day PCSOs vs. PCs
00:42:2300:40:02
00:11:12
00:40:06
00:00:00
00:07:12
00:14:24
00:21:36
00:28:48
00:36:00
00:43:12
00:50:24
PCSOs PCs
ExperimentalControl
Similar Appearance
Constable Police-Community SO
Reduction in offences between experimental & control areas
3994
3391
0
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4500
Control Experimental
Over 20 Replications in all(Braga et al 2012 Review)
• Mostly find same effects• No replication of Koper curve
(Peterboro and Birmingham coming)• No dosage-response curve• Biggest gap—displacement analysis
1. Vicinity effects 2. Individual offender effects
Falsifying Vicinity Displacement
David Weisburd David Weisburd
Vicinity Displacement?Weisburd, 2006: Jersey City
Not For Prostitution
Open-Air Drug Dealing
No Displacement of Drug Dealing
What about Offender Displacement?
• Washington DC• 2011• Hot Spot Campaign• Increased arrests• Large robbery decline• Matched control
areas• Quasi-experimental
design
University of MarylandDavid Mazeika
Arrests Went Up
Robberies Went Down(colours reversed)
No Vicinity Displacement
No Offender Displacement(Arrested N = 231 vs. 244)
Period Controls Target P
1.c. Tracking: The Next Frontier
• GPS Providers Failed to Design Reports• Camera providers may now do so• Most expensive investment in prevention• Subject to least accounting• Many studies show half of time in stations• Focus on hot spots doubles challenge• More time out • Team-by team competition
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6pm-8am 6pm-8am 6pm-8am 6pm-8am 8am-6pm 8am-6pm 8am-6pm 8am-6pmA B C D A B C D
Total Patrol Time
Num
ber o
f Min
utes
Total Patrol Time by Week in MinutesTeam CommandersTeam A) - 12487 A/Sgt. AliTeam B) - 13523 A/Sgt. RichardsonTeam C) - 13849 A/Sgt. TitusTeam D) - 13588 A/Sgt. Paul
Report Period- 12/1/14 to 25/1/14
Trinidad Police
0
1000
2000
3000
4000
5000
6000
7000
6pm-8am 6pm-8am 6pm-8am 6pm-8am 8am-6pm 8am-6pm 8am-6pm 8am-6pmA B C D A B C D
Total Patrol Time 5838 2773 3265 4637 4605 6496 5980 3164Total Patrol Geo-fence HS 1362 127 609 388 683 1289 1552 712
Num
ber o
f MIn
utes
Ratio of Patrols in and out HotSpots in MinutesTeam CommandersTeam A) - 12487 A/Sgt. AliTeam B) - 13523 A/Sgt. RichardsonTeam C) - 13849 A/Sgt. TitusTeam D) - 13588 A/Sgt. Paul
Report Period- 12/1/14 to25/1/14
Missing the Target
Will City Planners Apply Research?
• Will the key decisions be subjected to the Triple-T of evidence-based policy
• Will licensed premises, e.g., be tested with RCTs on concentrations?
• CCTVs? • Lighting? • Windows for eyes on the street?
Summary: We Know a Lot and Learn More Each Day,But Will Crime Prevention Professions Apply
This Growing Body of Research?
• Professions never defined themselves as dependent on research before
• Neither did medicine until early 1900s• Crime is century behind disease• But police are catching up fast• Other professions are slower• Thirst for better results is a great incentive• That’s why we’re all here!
THANK YOU
Lawrence W. ShermanInstitute of Criminology, Cambridge UniversityJerry Lee Centre of Experimental Criminology
24th February 2014
00.20.40.60.8
11.21.41.6
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