The thin blue line meets the big blue sky: perceptions of police legitimacy and public attitudes towards aerial drones

Police departments across the United States are now integrating new visual monitoring technology (e.g. unmanned aerial vehicles [UAVs or ‘drones’], body cameras) into routine police practices. Despite their potential use in multiple areas of proactive and reactive policing, public attitudes toward police use of UAVs, and visual monitoring technology overall, is mixed. As an extension of previous research, the current study uses a national survey to assess how well individuals’ perceptions about police legitimacy, effectiveness, and other criminal justice attitudes predict the level of public receptivity and opposition toward police UAV use in various contexts. The implications of these findings for public policy and law enforcement practices are discussed.     

Discrimination between sediment and soil samples for forensic purposes using elemental data: an investigation of particle size effects

This paper reports the results of an investigation to quantify variations in elemental concentrations amongst different particle size fractions obtained from a suite of sediment samples collected from the River Avon, UK. Concentrations of 49 elements determined by inductively coupled plasma spectrometry (ICP-AES and ICP-MS) were compared using conventional and multivariate statistical methods in order to assess compositional differences between different size fractions and between different samples. The results showed significant differences between different size fractions and the bulk sediments, but indicated that all of the size fractions considered (<150, 63-150, 20-63 and <20microm) provided an adequate basis on which to identify associations and differences between samples. It was concluded that, while in certain specific circumstances it may be most appropriate to make forensic comparisons based on a very narrowly defined particle size range, for the majority of purposes the <150microm fraction provides the best compromise between sample size requirements and data resolution.     

Development of a searchable major and trace element database for use in forensic soil comparisons

Forensic soil comparisons are normally undertaken on the basis of several physical, chemical and biological properties, but in all cases the interpretation of results is dependent on the availability of relevant contextual information. This paper summarises the results of major and trace element analyses performed using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma-mass spectrometry on the < 150 µm size fraction of 1896 soil samples collected in connection with forensic investigations in England and Wales between 1999 and 2007. A number of new methods are described which facilitate inter-sample comparison. Although the available data do not provide uniform geographical coverage they do provide useful information which can assist police search investigations and they provide valuable contextual information which aids the evidential assessment of soil evidence when used in court. There is considerable scope to improve the database by increasing the geographical coverage and increasing the number of soil attributes which are included.     

Elemental analysis of soil samples for forensic purposes by inductively coupled plasma spectrometry — precision considerations

Major and trace elemental composition provides a powerful basis for forensic comparison of soils, sediments and rocks. However, it is important that the potential ‘errors’ associated with the procedures are fully understood and quantified, and that standard protocols are applied for sample preparation and analysis. This paper describes such a standard procedure and reports results both for instrumental measurement precision (repeatability) and overall ‘method’ precision (reproducibility). Results obtained both for certified reference materials and example soils show that the instrumental measurement precision (defined by the coefficient of variation, CV) for most elements is better than 2–3%. When different solutions were prepared from the same sample powder, and from different sub-sample powders prepared from the same parent sample, the CV increased to c. 5–6% for many elements. The largest variation was found in results for certified reference materials generated from 23 instrument runs over an 18 month period (mean CV = c. 11%). Some elements were more variable than others. W was found to be the most variable and the elements V, Cr, Co, Cu, Ni and Pb also showed higher than average variability. SiO₂, CaO, Al₂O₃ and Fe₂O₃, Rb, Sr, La, Ce, Nd and Sm generally showed lower than average variability, and therefore provided the most reliable basis for inter-sample comparison. It is recommended that, whenever possible, samples relating to the same investigation should be analysed in the same sample run, or at least sequential runs.     

Elemental analysis of soil samples for forensic purposes by inductively coupled plasma spectrometry--precision considerations

Major and trace elemental composition provides a powerful basis for forensic comparison of soils, sediments and rocks. However, it is important that the potential 'errors' associated with the procedures are fully understood and quantified, and that standard protocols are applied for sample preparation and analysis. This paper describes such a standard procedure and reports results both for instrumental measurement precision (repeatability) and overall 'method' precision (reproducibility). Results obtained both for certified reference materials and example soils show that the instrumental measurement precision (defined by the coefficient of variation, CV) for most elements is better than 2-3%. When different solutions were prepared from the same sample powder, and from different sub-sample powders prepared from the same parent sample, the CV increased to c. 5-6% for many elements. The largest variation was found in results for certified reference materials generated from 23 instrument runs over an 18 month period (mean CV=c. 11%). Some elements were more variable than others. W was found to be the most variable and the elements V, Cr, Co, Cu, Ni and Pb also showed higher than average variability. SiO2, CaO, Al2O3 and Fe2O3, Rb, Sr, La, Ce, Nd and Sm generally showed lower than average variability, and therefore provided the most reliable basis for inter-sample comparison. It is recommended that, whenever possible, samples relating to the same investigation should be analysed in the same sample run, or at least sequential runs.     

Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry

Particle size is a fundamental property of any sediment, soil or dust deposit which can provide important clues to nature and provenance. For forensic work, the particle size distribution of sometimes very small samples requires precise determination using a rapid and reliable method with a high resolution. The Coulter trade mark LS230 laser granulometer offers rapid and accurate sizing of particles in the range 0.04-2000 microm for a variety of sample types, including soils, unconsolidated sediments, dusts, powders and other particulate materials. Reliable results are possible for sample weights of just 50 mg. Discrimination between samples is performed on the basis of the shape of the particle size curves and statistical measures of the size distributions. In routine forensic work laser granulometry data can rarely be used in isolation and should be considered in combination with results from other techniques to reach an overall conclusion.