Predictive Crime Mapping: Arbitrary Grids or Street Networks?

Objectives

Decades of empirical research demonstrate that crime is concentrated at a range of spatial scales, including street segments. Further, the degree of clustering at particular geographic units remains noticeably stable and consistent; a finding that Weisburd (Criminology 53:133–157, 2015) has recently termed the ‘law of crime concentration at places’. Such findings suggest that the future locations of crime should—to some extent at least—be predictable. To date, methods of forecasting where crime is most likely to next occur have focused either on area-level or grid-based predictions. No studies of which we are aware have developed and tested the accuracy of methods for predicting the future risk of crime at the street segment level. This is surprising given that it is at this level of place that many crimes are committed and policing resources are deployed.

Methods

Using data for property crimes for a large UK metropolitan police force area, we introduce and calibrate a network-based version of prospective crime mapping [e.g. Bowers et al. (Br J Criminol 44:641–658, 2004)], and compare its performance against grid-based alternatives. We also examine how measures of predictive accuracy can be translated to the network context, and show how differences in performance between the two cases can be quantified and tested.

Results

Findings demonstrate that the calibrated network-based model substantially outperforms a grid-based alternative in terms of predictive accuracy, with, for example, approximately 20 % more crime identified at a coverage level of 5 %. The improvement in accuracy is highly statistically significant at all coverage levels tested (from 1 to 10 %).

Conclusions

This study suggests that, for property crime at least, network-based methods of crime forecasting are likely to outperform grid-based alternatives, and hence should be used in operational policing. More sophisticated variations of the model tested are possible and should be developed and tested in future research.

     

Closing Off Opportunities for Crime: An Evaluation of Alley-Gating

A new situational crime prevention measure recently introduced into Great Britain involves the fitting of gates to alleyways running along the back of terraced properties to restrict access to local residents and reduce opportunities for offenders. A number of quantitative techniques were used to assess the success of the intervention in reducing burglary in the City of Liverpool. The results demonstrate that, relative to a suitable comparison area, burglary was reduced by approximately 37%, there was a diffusion of benefit to properties in the surrounding areas, and the scheme was cost beneficial with a saving of £1.86 for every pound spent. The analyses provide persuasive evidence that these reductions were attributable to the intervention. We argue that the methodological techniques demonstrated here can be applied more widely to crime prevention evaluations.     

"Promises and Pineapples": Post-First World War Soldier Settlement at Beerburrum, Queensland, 1916-1929

Queensland's post-First World War Soldier Settlement Scheme, begun with noble and optimistic intentions in 1916, officially terminated in 1929 after ignominious failure. There were a number of factors which contributed to the erosion and ultimate destruction of this phase of land settlement, but Commonwealth-State antagonism and the incompetence of many State agricultural advisers were certainly significant elements. Beerburrum, just north of Brisbane, was one of the largest groups of settlements which characterised Queensland's attempts to turn swords into ploughshares. Beerburrum soldier settlers and their families strove valiantly to extract a basic living in the face of overwhelming adversity, and an examination of their circumstances offers a valuable window into the trials and tribulations of the entire scheme.     

Unusual shotgun injury. Gas blowout of anterior head region

During a 6-month period, we encountered two examples of tight contact wounds of the temple region which were associated with ovoid, fairly regular, perforating wounds of the skull and overlying skin. These wounds were located between the eyes with the upper border near the glabella and the lower border near the level of the lower eyelids. There was no evidence that these wounds were entry wounds and in both cases the projectiles were still within the cranial cavity. Therefore, they were interpreted as gas blowout wounds. No similar cases have been found in the literature. Law enforcement personnel and pathologists should be aware of this rather rare blowout type of shotgun injury since it may be subject to various misinterpretations, including that of an entry wound.     

Quantitation of atenolol, metoprolol, and propranolol in postmortem human fluid and tissue specimens via LC/APCI-MS

Hypertension is a growing medical concern in the United States. With the number of Americans suffering from hypertension increasing, the use of antihypertensives such as beta-blockers is increasing as well. In fact, three beta-blockers - atenolol, metoprolol and propranolol - were among the 200 most prescribed medications in the United States in 2003. Pilots that successfully manage their hypertension can remain certified to fly. The Federal Aviation Administration currently designates approximately 8% of active pilots as "hypertensive with medication". The Civil Aerospace Medical Institute (CAMI) performs toxicological evaluation on victims of fatal aviation accidents. At CAMI beta-blockers are analyzed using gas chromatography with mass spectrometric detection. We have, however, recently developed a liquid chromatography with mass spectrometric detection (LC/MS) method for the simultaneous quantitation of three commonly prescribed beta-blockers, atenolol, metoprolol and propranolol. One advantage of our LC/MS method is the specificity provided by an ion trap MS. Utilizing an ion trap MS, we were able to conduct MS/MS and MS/MS/MS on each analyte. This method also eliminates the time-consuming and costly derivitization step necessary during GC/MS analysis. Additionally, by utilizing this novel method, any concerns about beta-blocker metabolite and/or sample matrix interference are eliminated. The limits of detection for this method ranged from 0.39 to 0.78 ng/mL and the linear dynamic range was generally 1.6-3200 ng/mL. The extraction efficiencies for each analyte ranged from 58% to 82%. This method was successfully applied to postmortem fluid and tissue specimens obtained from victims of three separate aviation accidents.