Targeting Missing Persons Most Likely to Come to Harm Among 92,681 Cases Reported to Devon and Cornwall Police

Funder: University of CambridgeAbstractResearch questionGiven the information available to Devon and Cornwall Police at the time when they received a missing person report, which knowable variables indicated increased odds of the person coming to serious harm?DataThe study examines all 92,681 missing reports received by Devon and Cornwall Police over 11 years from 2008 through 2019, for which 3481 (3.8%) persons came to harm, or about one in 27. Variables known at the time the report was filed included (A) risk levels estimated by police applying the College of Policing risk assessment template (high, medium, low), and (B) the missing person’s age, gender, in-care status, disability, dyslexia, learning disability, hearing or visual impairment, reduced mobility, mental illness, child sexual exploitation risk, reported suicidal, vulnerable adult status and previous reports of being missing.MethodsOdds ratios are used to estimate differences in likelihood of missing persons coming to harm in a series of single-variable tests. Matrices are used to assess the accuracy of the current risk assessment process used by police services in England and Wales, as applied in Devon and Cornwall. Limited multivariate analysis was undertaken.FindingsApplication of the current College of Policing protocol for risk assessment by subjective professional judgements yields substantial error rates, with 89% of the predicted high risk cases having no actual harm and 59% of cases with actual harm after not being predicted as high risk. The odds of harm based on single variables examined are highly conditional on age and gender as third factors. Both men and women over 18 are 4 times more likely to be harmed (6.8%) than those under age 18 (1.7%).ConclusionsThis study casts substantial doubt on the accuracy of the current subjective risk assessment process for missing persons. As the authorizing body for Approved Professional Practice, the College of Policing could use this evidence to endorse further development and implementation of a multivariate evidence-based risk assessment tool for missing persons that takes into account the age and gender of the missing person as well as all other factors in a single forecasting model.</jats:sec

Noise suppression using symmetric exchange gates in spin qubits

We demonstrate a substantial improvement in the spin-exchange gate using symmetric control instead of conventional detuning in GaAs spin qubits, up to a factor-of-six increase in the quality factor of the gate. For symmetric operation, nanosecond voltage pulses are applied to the barrier that controls the interdot potential between quantum dots, modulating the exchange interaction while maintaining symmetry between the dots. Excellent agreement is found with a model that separately includes electrical and nuclear noise sources for both detuning and symmetric gating schemes. Unlike exchange control via detuning, the decoherence of symmetric exchange rotations is dominated by rotation-axis fluctuations due to nuclear field noise rather than direct exchange noise.Comment: 5 pages main text (4 figures) plus 5 pages supplemental information (3 figures

Victim-Offender Overlap in Violent Crime: Targeting Crime Harm in a Canadian Suburb

Funder: University of CambridgeAbstract Research Question To what extent are victims of violent crime also offenders, and vice versa, with what concentrations of total crime harm across each person who has ever been reported as both a victim and an offender within the study period? Data We analyse 27,233 unique individuals who were the subject of violent crime reports to the Peel Regional Police Service in Canada, either as offenders, victims, or both, for crimes reported between January 1, 2014, and December 31, 2016. Each individual linked to a violent crime in this period was tracked for the 730 days subsequent to the first crime report naming them. Methods We coded each crime with the Canadian Crime Severity Index (CCSI) to calculate victimization and offending harm totals across all incidents for each individual. We then computed each individual’s ratio of total CCSI from victimization to total CCSI from victimization. Based on the distribution of these ratios of CCSI from all offending to all victimization, we show how police can distinguish three categories of victim-offenders (VOs): predominant victims (PVs), predominant offenders (POs), and balanced victim-offenders (BVOs), as well as the single-category absolute offenders (AOs) and absolute victims (AVs). Findings Across all 27,233 individuals tracked, 17,138 (64%) appeared first as victims, and 10,095 (36%) appeared first as suspects. Of those appearing first as victims, 997 (6%) are linked to a violent crime as an offender within 730 days. Among those appearing first as offenders, 1019 (10%) are subsequently reported as victimized within 730 days. The total of this combined group (VOs) = 1665 individuals (6% of the entire population). Using a 3.5:1 ratio of victim to offender harm, we subdivide the 1665 VOs further into 322 predominant victims, 280 predominant offenders, and 1063 balanced victim-offenders. The 20% of individuals (n = 5455) with highest harm are linked to 71% of overall harm. On average, predominant offenders (who have also been victimized) are associated with 2.7 times as much harm as absolute offenders, and predominant victims (who have also been offenders) have three times as much harm as absolute victims. Conclusions This research shows how combining records of victimization and offending to target higher harm levels with greater potential benefits for police investments in harm reduction and prevention. </jats:sec

Focusing monochromator and imaging-plate camera for grazing-incidence diffraction studies of thin films

A multiple-imaging-plate detector system and focusing monochromator have been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett films by grazing-incidence X-ray diffraction (GIXD). The monochromator described here combines fixed-exit-beam height with sagittal focusing of the second crystal. The design is similar to that of Matsushita et nl. [Matsushita, Ishikawa & Oyanagi (1986). Nucl. Instrum. Methods, A246, 377-379], with the exception that the motion of the first crystal is achieved via a computer-controlled X-Y translation table rather than a set of cams. The second crystal is a ribbed Si(111) wafer mounted in a four-point bending mechanism. The first reported application of imaging plates to a GIXD study was carried out by our group and proved to be very successful in the determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of this system, an imaging-plate camera was designed and built which can accommodate up to 13 imaging plates (40 x 20 cm) inside the vacuum chamber of the main diffractometer at the Australian Beamline at the Photon Factory

Coherent multi-spin exchange coupling in a quantum-dot spin chain

Heisenberg exchange coupling between neighboring electron spins in semiconductor quantum dots provides a powerful tool for quantum information processing and simulation. Although so far unrealized, extended Heisenberg spin chains can enable long-distance quantum information transfer and the generation of non-equilibrium quantum states. In this work, we implement simultaneous, coherent exchange coupling between all nearest-neighbor pairs of spins in a quadruple quantum dot. The main challenge in implementing simultaneous exchange couplings is the nonlinear and nonlocal dependence of the exchange couplings on gate voltages. Through a combination of electrostatic simulation and theoretical modeling, we show that this challenge arises primarily due to lateral shifts of the quantum dots during gate pulses. Building on this insight, we develop two models, which can be used to predict the confinement gate voltages for a desired set of exchange couplings. Although the model parameters depend on the number of exchange couplings desired (suggesting that effects in addition to lateral wavefunction shifts are important), the models are sufficient to enable simultaneous and independent control of all three exchange couplings in a quadruple quantum dot. We demonstrate two-, three-, and four-spin exchange oscillations, and our data agree with simulations.Comment: 9+10 pages, 5+5 figure

Comparing probability of police officer dismissals in London between misconduct hearings chaired by chief officers and legally qualified chairs

We examined all 234 standard (excluding “special” or “accelerated”) misconduct hearings resolved by the MPS in all 22 months prior to the first hearings chaired by Legally Qualified Chairs (LQCs) in 2016, and in the first 22 months after the first LQC hearings, for a total of 44 months. We limited the time period after LQCs began to chair hearings to the 22 months before a further change in 2018 allowed officers to resign (without permission) while charges were still pending against them (thus averting being dismissed). A total of 142 standard misconduct hearings were chaired by Chief Officers, and 92 cases were chaired by LQCs. Of the 142 Chief Officer cases, 20 cases were heard after the advent of LQC cases, because Chief Officers were still required to chair hearings in relation to misconduct investigations initiated under regulations in effect prior to 2012

Police, public, and offender perceptions of body-worn video: a single jurisdictional multiple-perspective analysis

Objectives. Police, public, and offender survey responses from a single jurisdiction give a multiple-perspective insight into the use of body-worn video (BWV) cameras by police. Methods. Police attitudinal data was collected from before (n = 190), during (n = 139), and at the conclusion (n = 221) of a BWV implementation trial. Public attitudes were collected at the conclusion of the BWV implementation trial via online survey (n = 995 respondents) and intercept survey (n = 428 respondents). Offender attitudes (n = 302) were collected in police custody over a 6-month period immediately preceding the BWV trial. Results. The extent to which police felt BWV influenced their behavior tempered during the trial. All three perspectives were supportive of the use of BWV. The public who had encountered BWV-wearing officers and the offender sample indicated limited belief that BWV would reduce bad behavior. There was also clear contention about the policy and practice decisions around recording. Conclusions. These findings have significance for BWV trials, commenting on the importance of (a) collecting police attitudes at multiple points, (b) separating the attitudes of public who did encounter police wearing BWV, and (c) data collection and policy for evaluation outcomes