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Journal Cover Cambridge journal of evidence-based policing
  [28 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  [2352 journals]
  • Police Attempts to Predict Domestic Murder and Serious Assaults: Is Early
           Warning Possible Yet'
    • Authors: Sara Thornton
      Abstract: Research Question What facts known to police, if any, could have predicted the 118 domestic and family murders and near-murders in the Thames Valley (UK) police area over a recent three-year period' Data Thames Valley Police records were examined for 118 victims and 120 offenders in all 118 cases of “deadly” domestic violence: murder, attempted murder, manslaughter, and grievous bodily harm with intent in calendar years 2007, 2008 and 2009. Police National Computer (PNC) and other records of police contact with those persons prior to the cases identified for this prediction study were also coded, as well as the PNC records of a case-control sample of 150 male and 100 female offenders in less serious violent crimes. Local police risk assessments, including the DASH protocol, were coded for deadly violence cases with prior police contact. Methods Risk assessments made during prior police contacts with domestic violence cases during the time period were coded for accuracy of forecasts. Characteristics of offenders and victims in deadly violence were also compared to characteristics of the case-control sample, calculating the relative-risk ratios between the two groups for the presence of factors that further research could explore as possible predictors of deadly domestic violence. Findings In 55% of deadly violence cases, there was no prior recorded contact by police with the victim; a further 21% of victims had only one prior police contact. Not one of the 13 murder cases with any prior police contact had ever been assessed by responding officers as “high risk” based on DASH or its predecessor, for a 100% false negative rate of prediction on risk of murder and an 89% false negative rate for any deadly violence (only 6 cases with prior contact had been classified as high risk). In contrast, during the same time period, 2721 other domestic violence cases yielded “high-risk” assessments but were not actually followed by deadly violence. Yet the case control study found male offenders who committed serious domestic assaults were over three times more likely than other violent offenders to be have had markers of suicidal tendencies. Conclusions Predicting deadly domestic violence based on intelligence from prior police contacts does not appear possible at present, given these findings that less than half of these cases had prior police contact, and that when contact did occur, the relationships were assessed by the DASH protocol or its predecessor as not high risk in 89% of those cases. A more promising predictor for male offenders in these cases, even without prior contact, may be a prior marker for suicide (ideation, threats or attempts), but use of that marker requires further research on the extent to which it can be identified before the deadly violence occurs, either from police contacts or other sources, so that more intensive efforts can be undertaken to prevent deadly violence in the truly high-risk cases.
      PubDate: 2017-08-28
      DOI: 10.1007/s41887-017-0011-1
  • Introduction—Key Facts About Domestic Abuse: Lessons from Eight
    • Authors: Lawrence Sherman; Heather Strang; Denis O’Connor
      PubDate: 2017-08-23
      DOI: 10.1007/s41887-017-0014-y
  • Intimate Partner Homicide in England and Wales 2011–2013: Pathways to
           Prediction from Multi-agency Domestic Homicide Reviews
    • Authors: Eamonn Bridger; Heather Strang; John Parkinson; Lawrence W. Sherman
      Abstract: Research Question What pathways to more accurate prediction of intimate partner homicide (IPH) can be found by reviewing two years of official Domestic Homicide Reviews in England and Wales' Data This study conducted a detailed review of investigative source material, police database information and the official independent author reviews of the 188 cases of intimate partner homicide recorded in England and Wales between April 2011 and March 2013. Methods Descriptive analytical techniques were used to explore the prevalence of various characteristics of victims, offenders and relationships in these cases, with special attention given to offender suicide ideation as a precursor to the crimes. Findings Offenders in these cases were 86% male, with high rates of both chronic substance abuse (61%) and prior reported offending (50%) against their homicide victim. The most disproportionately prevalent characteristic appears to be that 40% of the male offenders were known by someone, but often not to police, as suffering suicidal ideation, self-harm or attempted suicides. The prevalence of that marker, while not measureable in the general population, is over four times higher than the pre-offence police indications of suicidal tendencies across 80 domestic homicides in Leicestershire (Button et al., 2017). Conclusions It is plausible that many more intimate partner homicides might be accurately predicted, and perhaps prevented, with more public investment in obtaining data on suicidal indicators and more proactive treatment of domestic abuse offenders known to suffer suicidal tendencies.
      PubDate: 2017-08-22
      DOI: 10.1007/s41887-017-0013-z
  • Integrated case management of repeated intimate partner violence: a
           randomized, controlled trial
    • Authors: Jonathan Goosey; Lawrence Sherman; Peter Neyroud
      Abstract: Research Question Can integrated case management by a multi-agency partnership of the relations between offenders and victims with repeated incidents of intimate partner violence (IPV) reduce the frequency or severity of harm from that violence' Data Three batches of 60 IPV dyads were enrolled in a trial, with data collected on services delivered to them and police records for 2 years before and 2 years after random assignment to treatment and control groups. Methods The study measured the delivery of all three elements of treatment offered: (1) victim support through Berkshire Women’s Aid, (2) one-to-one perpetrator counselling through motivational interviewing techniques and (3) follow-up visits to the home addresses of perpetrators and victims. The outcomes for each couple in severity of harm were compared in a before-after, difference-of-differences analysis of Cambridge Crime Harm Index scores. After-only frequency of non-criminal domestic conflict events was also compared. Findings Delivery of programme elements was highly variable, but more intense in the treatment group than in control, especially in terms of police visits to offenders (T = 60%, C = zero). Mean difference between 24 months of post-random assignment and the 24 months baseline period for C cases was an increase of 4.15 Cambridge Crime Harm Index (CHI) prison days, while T cases had a mean change of 8.85 fewer CHI days in prison in post-assignment than in baseline. This difference was significant with outliers removed, but not with two control group baseline cases included. There was also a substantially higher rate of frequency of non-crime events in the 24 months after random assignment in T (112) than in C (85). Conclusions The overall effect of the programme appeared to have been beneficial, as measured by the Crime Harm Index. The evidence cannot specify how much of that benefit was caused by the more consistent police visits to offenders versus other elements of the programme for both victims and offenders.
      PubDate: 2017-08-18
      DOI: 10.1007/s41887-017-0012-0
  • Predicting Domestic Homicides and Serious Violence in Dorset: a
           Replication of Thornton’s Thames Valley Analysis
    • Authors: Robert Chalkley; Heather Strang
      Abstract: Research Question What facts known to police, if any, could have predicted the 107 domestic and family murders and near-murders in Dorset (UK) police area over a recent 7-year period, using methods identical to Thornton’s (2011, 2017)' Data The data were gathered from all 107 cases of domestic murders, manslaughter, attempted murder or grievous bodily harm with intent in Dorset between April 2009 and March 2015, plus a matched control sample of 214 arrestees for less-deadly violent offences. Methods Replicating Thornton’s Thames Valley analysis, two methods were used: (1) calculating errors in predictions from previous risk assessments using the UK’s DASH (Domestic Abuse, Stalking and Harassment) risk assessment protocol and (2) making a case-control comparison of Thornton’s risk factors between the deadly domestic violence cases in Dorset to a Dorset sample of victims and offenders in all violence cases during the same time period. Findings False negative risk assessments were found in 67% of the deadly violence cases with prior police contact (45 of 67) not classified by DASH as ‘high risk.’ The false positives in the same time period totalled 12,279 cases of no serious harm among 12,301 cases receiving high risk assessments, for a 99% false positive rate. Possible alternative predictors were found in differences between deadly offenders and controls, both male and female, although it is not known whether these variables were added to the records before or after the deadly violence event. Male offenders in deadly violence cases were 120% more likely to have their police records note a self-harm warning, 20% more likely to have a suicide warning, yet only half as likely to have a mental health warning as control males. Female offenders in deadly violence cases were 355% more likely to have a weapons warning on file, 244% more likely to have a mental health warning and 146% more likely to have a drugs warning than female control case offenders. Conclusions The current risk assessment tool (DASH) failed to predict the majority of deadly domestic violence cases over 6 years in Dorset. Other factors could do better, but more research is required before highly accurate forecasting tools can be applied to help save the lives of more domestic abuse victims.
      PubDate: 2017-08-03
      DOI: 10.1007/s41887-017-0010-2
  • Predicting Domestic Homicide and Serious Violence in Leicestershire with
           Intelligence Records of Suicidal Ideation or Self-Harm Warnings: a
           Retrospective Analysis
    • Authors: Ian M. D. Button; Caroline Angel; Lawrence W. Sherman
      Abstract: Research Question Does prior information retained in police intelligence records about an offender’s suicidal tendencies help to predict a future domestic homicide or attempted homicide' Data Records on 158,379 arrestees in 1997–2015 were examined for suicidal or self-harm warnings by date of entry and compared to 620 offenders identified in cases of domestic homicides or serious violence over the same time period. Methods The percentage of offenders in domestic homicide and serious violence cases who were known to have reported suicidal ideation prior to those crimes was compared to the overall percentage of arrested persons who had such reports. Findings Of the total 620 deadly violence offenders, 125 had a marker for suicide or self-harm, of which 35 (5.6%) were posted prior to the deadly domestic violence. Of the 80 homicide cases (excluding grievous bodily harm), 7 had suicide or self-harm markers prior to the homicidal offence, for a rate of 8.75%. These rates compare to an overall marker rate among the 158,379 arrestees in the time period studied, of whom 7,241 were identified as holding a warning marker at the point of data collection for this study in 2016, which equated to only 5% of the group, of which an estimated 38% would have occurred prior to a crime (2,752 cases), or 1.7% of the 158,379. By that metric, it is three times more likely that offenders charged with an act of deadly domestic violence had prior suicidal warning markers than offenders not charged with such crimes (5.6/1.7 = 3.3), and 5.2 times more likely for homicide offenders to have a prior marker than for all arrestees. Conclusions Police intelligence system markers for suicide or self-harm can provide valuable information for building more accurate prediction models for domestic homicide and serious assaults.
      PubDate: 2017-07-31
      DOI: 10.1007/s41887-017-0009-8
  • Targeting Escalation of Intimate Partner Violence: Evidence from 52,000
    • Authors: Lee Barnham; Geoffrey C. Barnes; Lawrence W. Sherman
      Abstract: Research Question Does the severity or frequency of intimate partner violence or abuse reported to police increase over time, once a unique perpetrator-victim couple has come into contact with police in Thames Valley, UK' Data A total of 140,998 recent (non-historical) incidents of intimate partner violence or abuse reported to Thames Valley Police in 2010–2015 were identified, with 52,296 unique perpetrators for whom a standard 731-day observation period was possible after each perpetrator’s first incident was reported in the intake period from 1 January 2010 through 31 December. Duplicate entries were eliminated and standard eligibility criteria were assured by data cleaning from the NICHE records management system of Thames Valley Police. Methods All non-crime incidents or reports of crime against intimate partners were coded by the Cambridge Crime Harm Index (CHI) with the sum of total days of recommended imprisonment for each offence (as the guideline starting point for sentencing) summed across all offences for each offender (Sherman et al. in Policing, 10(3), 171–183, 2016), with CHI scores for each successive incident plotted in sequence. Prevalence and frequency of repeat police contacts were also computed for each perpetrator, as well as the conditional probability of each new offence given the number of prior offences. Findings Most perpetrators identified in the 52,296 initial reports (77.6%) had no report of crime after the initial report. A further 21.2% had crime harm totals of less than 10 days of recommended prison time, with only 893 (1.7%) of the total universe of 4 years’ worth of perpetrators who had a reported crime harm total over offences with a recommendation of over 10 days sentencing in the 731-day observation period. A slightly larger ‘power few’ of 3% of perpetrators accounted for 90% of total intimate partner abuse crime harm inflicted by all perpetrators, while 97% of perpetrators produced only 10% of total crime harm. Overall, amongst the few who had numerous repeat incidents, there was increasing frequency but no evidence of increasing seriousness of harm caused to victims. The 100 most harmful offenders in 2010 maintained a high (but greatly decreased) level of harm in 2011, but on average were very low harm offenders in 2012–2015. Conclusions This analysis suggests that the intimate partner abuser population is highly segmented in Thames Valley, with a small power few inflicting most of the harm. While the most serious offenders may remain difficult to identify prospectively, any valid prediction model could help to prevent a substantial amount of crime harm against intimate partners. Investing in such prediction methods may do more to help victims than an undifferentiated strategy putting most resources into low-risk cases.
      PubDate: 2017-07-31
      DOI: 10.1007/s41887-017-0008-9
  • Reducing the Harm of Intimate Partner Violence: Randomized Controlled
           Trial of the Hampshire Constabulary CARA Experiment
    • Authors: Heather Strang; Lawrence Sherman; Barak Ariel; Scott Chilton; Robert Braddock; Tony Rowlinson; Nicky Cornelius; Robin Jarman; Cristobal Weinborn
      Abstract: Research Question Among Southampton-area males arrested for and admitting to low-risk intimate partner violence as a first domestic offence and receiving a conditional caution, did a randomly assigned requirement to attend (with four to seven other male offenders), two weekend day-long Cautioning and Relationship Abuse (CARA) workshops led by experienced professionals reduce the total severity of crime harm relative to a no-workshop control group' Data Eligible offenders (N = 293) were randomly assigned to the CARA workshop attendance requirement (n = 154) or to the no-workshop requirement (n = 139), with 91% of all cases receiving treatment as randomly assigned. Each offender’s records of police contact were tracked for exactly 365 days after the date of random assignment. Methods All repeat arrests or complaints of crime naming the 293 randomly assigned offenders were coded by the Cambridge Crime Harm Index (CHI) as the primary outcome measure for each offender (Sherman et al. in Policing, 10(3), 171–183, 2016), with the sum of total days of recommended imprisonment for each offence (as the guideline starting point for sentencing) summed across all new offences, with both domestic and non-domestic relationships to their victims. Prevalence and frequency of repeat contact were also computed. All analysis was done by intention-to-treat. Findings Offenders assigned to the workshop group were re-arrested for crimes with a total CHI value that was 27% lower than for re-arrests of offenders assigned to the control group (P = .011). The CARA workshop group members were arrested for crimes totalling an average of 8.4 days of recommended imprisonment under English sentencing guidelines, compared to an average of 11.6 days per offender assigned to the control group, the equivalent of 38% more harm without the workshop than with it. The effect size was much stronger, however, in the first study period of high caseflow (72% reduction in CHI, P = .001) than in the second period (21% reduction in CHI, P = .178). Frequency of re-arrest for domestic abuse (21% lower for workshop-assigned group) and prevalence (35% lower for workshop-assigned group) also favoured the CARA workshop group. Conclusions The results of this 1-year follow-up analysis suggest that the CARA workshops are an effective way to reduce the future harm of domestic abuse among first offenders who admit their crime, although effect size may vary over time. Given the highly restrictive eligibility criteria for the programme, these findings provide an evidence-based reason for testing the same treatment among a larger proportion of all first-offender arrests for domestic abuse.
      PubDate: 2017-07-17
      DOI: 10.1007/s41887-017-0007-x
  • Targeting Escalation and Harm in Intimate Partner Violence: Evidence from
           Northern Territory Police, Australia
    • Authors: Jeanette Kerr; Carolyn Whyte; Heather Strang
      Abstract: Research Question Does analysis of intimate partner violence (IPV) among Aboriginal and non-Aboriginal couples in the Northern Territory (NT), Australia, reveal any predictable escalation in frequency or severity of harm over a 4-year observation period' Data We examined all 61,796 incidents of IPV recorded by the NT Police for 23,104 unique couples (‘dyads’), over the 5-year period from 1 January 2010 to 31 December 2014. For purposes of analysing changes over time in frequency and harm, we used standardised observation periods (generally 4 years) from first incident to end of observations. Methods Each IPV incident was re-classified by crime type using the penal code of England and Wales, in order to measure the severity of harm in NT with the Cambridge Crime Harm Index (CHI). The CHI scores were used to test for patterns of concentration and escalation, based on the total days of recommended imprisonment for each offence type, summed across all offences of that type for the entire sample. Findings The findings were sharply split between Aboriginal and White dyads. While there was no evidence of escalation in either frequency or severity of IPV incidents in the White dyads, there was substantial evidence of escalation among Aboriginal offenders with three or more incidents in a 4-year period. Less than 2% of White offenders (2 of 111) had three or more incidents in 4 years, compared to 32.4% of Aboriginals (N = 105 out of 355 offenders). For those couples of both races known by police to have two or more incidents, there was a strong pattern of escalation in the frequency and seriousness of offending for up to 20 incidents over 4 years. While 66% of couples had desisted by year 3 with no further reports that year or the next, among the 34% of couples (N = 3621) persisting into year 3 the probability of a new incident by year 4 was 99.9%. Similarly, the time between incidents for these repeaters declined with each new incident, indicating an increase in frequency. Severity of harm also rose with repeated incidents, from 0.6 of expected Cambridge CHI value per dyad among couples with 1 to 5 incidents over 4 years to 3.82 times higher than expected value per dyad among those couples observed to have 16–20 incidents over 4 years—six times more harm among couples (almost entirely Aboriginals) with the highest frequency of incidents than among couples with the lowest frequency. Conclusions This targeting analysis confirms other research that shows no escalation in frequency or severity of domestic abuse among predominantly White European populations. Yet it also provides the first systematic test of the escalation hypothesis about IPV reported to police among Australian Aboriginal dyads. That evidence provides a strong basis in evidence for developing a two-track policy for policing IPV in Australian areas with substantial Indigenous populations. Track 1 would serve dyads (of either race) presenting for the first or second time, for whom a light touch may generally be sufficient. Yet any couple known to have had two or more prior offences could receive a far more intensive strategic investment, including the testing of new strategies for prevention of escalation in harm or frequency of IPV. Yet because this pattern of escalation is found only in a minority of Aboriginal dyads, it is important to base policy on evidence-based targeting of dyads with prior occurrences rather than race.
      PubDate: 2017-07-05
      DOI: 10.1007/s41887-017-0005-z
  • Cynthia Lum, Christopher S. Koper: Evidence-Based Policing: Translating
           Research into Practice
    • Authors: Jamie Hobday
      PubDate: 2017-06-27
      DOI: 10.1007/s41887-017-0006-y
  • 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
    • 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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