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Journal Cover Cambridge journal of evidence-based policing
  [25 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 2520-1344 - ISSN (Online) 2520-1336
   Published by Springer-Verlag Homepage  [2345 journals]
  • The “Power Curve” of Victim Harm: Targeting the Distribution of Crime
           Harm Index Values Across All Victims and Repeat Victims over 1 Year
    • Authors: Gavin Dudfield; Caroline Angel; Lawrence W. Sherman; Sarah Torrence
      Abstract: Research Question Is the vast majority of crime harm in one police force area over 1 year suffered by a small percent of all known victims, with many of those most-harmed victims suffering repeated and perhaps preventable crimes if more police resources were to be invested in them' Data All 30,244 crimes recorded as committed against all 25,831 persons with one or more known victimization reported between 1 June 2015 and 31 May 2016 in Dorset, UK. Methods Each criminal event was weighted by the Cambridge Crime Harm Index (CHI) method, using the number of days of imprisonment recommended by the Sentencing Council for England and Wales as the “starting point” for sentencing offenders convicted in each crime category. Regardless of whether an offender was detected or convicted, each crime was coded with the starting point penalty. The total number of days assigned was then summed across all crimes in Dorset and individually for each victim, with the victims rank-ordered from highest to lowest number of total days of recommended imprisonment assigned to each (the Cambridge CHI value). Findings Under 4% of victims (968) suffered 85% of the CHI value of total days of recommended punishment for the crimes against all victims, with sex offences and robbery contributing almost two thirds of total CHI harm (63%).Almost one third (29%) of the harm were committed against repeat victims, including their first victimization within the 1-year period. Slightly over half of the harm against those repeat victims (57% of the harm across 4211 victimizations against repeat victims) occurred after their first victimization, equal to 15% of total harm to all victims that year. Just 256 repeat victims, comprising 1% of all victims, suffered 26% of total victim harm, ranging from 2 to 14 victimizations per person. The mean CHI value for each of these repeat victims was 1396 days (∼4 years) of recommended imprisonment for the totals of anywhere from 2 to 14 crimes against each member of this beleaguered 1%. The overall concentration of harm in a tiny fraction of all victims forms a “disproportionality ratio” of 15:1, with the “power few” most-harmed 4% of victims suffering 15 times more harm than expected if all victims suffered equal harm, with the highest disproportionality ratios of any offence types, 19 to 1 for sex offences and 5 to 1 for robbery. Conversely, the total CHI value of thefts was 0.143:1 or only one seventh of what it would have been with an equal distribution of harm across all criminal events. The ratio for burglary was 0.25:1, and even for violence (0.67:1), there was 33% less harm than expected for equal harm by crime type. Conclusion The vast majority of crime harm in one UK police force area over 1 year was suffered by a small percent of all known victims, with 15% of total harm occurring as repeat victimizations. This finding demonstrates the value of better algorithms for predicting repeat victimizations to allocate prevention resources, starting with the Cambridge CHI value of each first offence against each victim.
      PubDate: 2017-05-26
      DOI: 10.1007/s41887-017-0001-3
       
  • Frequency Vs. Length of Hot Spots Patrols: a Randomised Controlled Trial
    • Authors: Simon Williams; Timothy Coupe
      Abstract: Research Question Do shorter but more frequent patrol visits to the same crime hot spots reduce daily crime and anti-social behaviour (ASB) totals more effectively than less frequent but longer patrols, if the total time that police are present each day is held roughly constant' Data GPS measures from patrol officer body-worn radios tracked the time each officer spent within seven geo-fenced crime “hot spots” of 150 × 150 m, summing the number of both individual officer-minutes and patrol-minutes (with one or more officers present simultaneously) per day per hot spot, as well as number of visits and minutes per visit. Activity reports were used to detect the simultaneous presence of more than one officer, yielding the key independent variables of number and length of patrol visits in which one or more police officers were present. The dependent variable was total reports of crime and anti-social behaviour (ASB) identified within the hot spot boundaries each day of the experiment. Method All seven hot spots of crime and ASB were randomly allocated each day to one of two patrol duration conditions for a period of 100 days (43 “short” visit days and 57 “long” visit days) between June and November 2015, with patrol time measures reported back to officers on the number and length of patrols conducted daily. The long visit model required three visits daily of 15 min duration each; the short visit model required nine visits daily of 5 min each. On all days, a target of 45 min of total patrol time was required. Results Actual patrol delivery measured by GPS and activity reports produced a mean of just over 24 patrol-minutes (of one or more officers present) on “long” days and just under 26 min on “short” days, so that dosage was approximately held constant to test the independent effect of more or fewer visits. The treatment as delivered on “long” days was a mean of 2.5 visits averaging 9.6 min each; on “short” days, the same officers delivered a mean of 5 visits averaging 5.2 min each. The less-frequent long visit model was more effective than the more-frequent short visit model, with mean counts of crime and ASB incidents 19.51% lower on long visit days =0.697 incidents per day compared to 0.561 incidents per day on short visit days (d = −0.175; p = 0.018). Conclusion Controlling for the total patrol time spent at a hot spot each day, the difference between 2.5 longer visits and 5 shorter visits causes about 20% less crime when longer visits are delivered. These findings of the deterrent effect of increasing patrol visit length by 85% are consistent with Koper’s (1995) correlational observation that longer units of 10–15 min duration appeared optimal in creating a residual deterrent effect at a hot spot immediately after police leave the vicinity. Although this study cannot distinguish between crime reductions immediately after vs. long after police have left the scene, this is the first experiment to randomly assign a substantial difference (twice as many) in the number of visits daily to a hot spot, with almost twice as much time per visit when fewer visits are made. The use of random assignment of two different patrol models with the same total time in the same seven geographic units gives great confidence that using that time in fewer visits of longer duration causes less crime and anti-social behaviour than more visits of shorter duration.
      PubDate: 2017-05-12
      DOI: 10.1007/s41887-017-0003-1
       
  • Editorial Policies
    • Authors: Lawrence W. Sherman
      PubDate: 2017-05-08
      DOI: 10.1007/s41887-017-0004-0
       
  • Frequency Versus Duration of Police Patrol Visits for Reducing Crime in
           Hot Spots: Non-Experimental Findings from the Sacramento Hot Spots
           Experiment
    • Authors: Renée J. Mitchell
      Abstract: Research Question Was the effect of police patrols reducing crime and disorder in the Sacramento Hot Spots Experiment (SHSE) more strongly associated with the average frequency of patrol visits or the total duration of all visits combined' Data Two independent measures of patrol were used to analyze initial and new data on the 42 hot spots that Telep et al. (2014) studied in 21 matched pairs for the SHSE: Computer-Assisted Dispatch (CAD) records on the number of and duration of patrol visits to each hot spot (initial data), and Automatic Vehicle Locator (AVL) (new) data on total patrol time within the “geo-fenced” area of each hot spot. The patrol measures were linked to two outcome measures at each hot spot. Part I crime reports and citizen-generated Calls for Service (CFS) records for events occurring within the hot spot street address boundaries. Methods All SHSE pairs of hot spots were examined as a meta-analysis of 21 experiments for differences in frequency and total duration of patrols. Then all 42 hot spots were examined for correlations between outcome measures and CAD data on frequency and duration, plus AVL data on duration [AVL data could not reliably measure frequency of discrete patrol visits]. Findings The SHSE created large mean differences between experimental and control conditions in both frequency and total duration of patrols, which were highly correlated (r = .9). Correlations of CAD measures of before-during increases in frequency, but not duration, of patrols across all 42 hot spots predicted somewhat fewer event counts of both outcome measures: crime reports (r = −.273, one-tailed p = .04) and CFS (r = −.234, one-tailed p = .068). In contrast, AVL data on before-during increases in duration showed somewhat less crime with more duration of total patrol time (r = −.231, one-tailed p = .07), but no effect of more duration on CFS. Conclusions Based on the analysis of CAD data, police may be able to reduce crime and disorder more effectively by making more frequent patrols in each hot spot, while reducing the total time of all patrols. Contrary to the policy conclusion from the Koper (1995) Curve, the CAD findings may suggest there is greater benefit in having more visits of under 15 min rather than having fewer visits that all last from 10 to 15 min each. Yet, the evidence from this study is mixed. The CAD finding is contradicted by this study’s AVL data analysis, which show that greater increases in total patrol duration did predict somewhat fewer crimes (but not CFS). Since both the CAD and AVL findings are correlational rather than based on random assignment of frequency and duration, field experiments are now needed to provide more definitive answers to the research question.
      PubDate: 2017-04-05
      DOI: 10.1007/s41887-017-0002-2
       
 
 
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