Ink Dating Using Thermal Desorption and Gas Chromatography/Mass Spectrometry: Comparison of Results Obtained in Two Laboratories

An ink dating method based on solvent analysis was recently developed using thermal desorption followed by gas chromatography/mass spectrometry (GC/MS) and is currently implemented in several forensic laboratories. The main aims of this work were to implement this method in a new laboratory to evaluate whether results were comparable at three levels: (i) validation criteria, (ii) aging curves, and (iii) results interpretation. While the results were indeed comparable in terms of validation, the method proved to be very sensitive to maintenances. Moreover, the aging curves were influenced by ink composition, as well as storage conditions (particularly when the samples were not stored in “normal” room conditions). Finally, as current interpretation models showed limitations, an alternative model based on slope calculation was proposed. However, in the future, a probabilistic approach may represent a better solution to deal with ink sample inhomogeneity.     

光谱成像在物证检验中的初步实验研究

目的研究运用光谱成像技术进行物证形态检验的可能性和方法。方法比较相同条件下使用普通照相方法与光谱成像方法拍摄多种痕迹物证的效果。结果光谱成像检验的能力和效果都具有明显优势。结论光谱成像检验技术的出现使物证形态检验学的发展进入了一个崭新的阶段。     

红外线照射谷物表面杀菌的研究

利用红外线对小麦和大豆的表面进行照射杀菌,比较不同红外线照射条件对附着生菌数、杀菌效果及对品质的影响。结果表明:红外线照射可在较短时间内杀死对热比较敏感的微生物,照射1s后生存比急剧下降,而接续的照射由于对热抵抗性较强的微生物存在,生存比的下降缓慢。对品质分析和发芽试验也证明:照射后水分含量变化不明显,小麦在2%左右,大豆没有发生变化,对谷物内部品质几乎没有影响。红外线照射引起微生物的死亡不是由谷物表面受热后再向微生物传导加热,而是微生物直接受红外线辐射的热致死的。     

Developmental Times of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) at Constant Temperatures and Applications in Forensic Entomology

The characteristic life stages of infesting blowflies (Calliphoridae) such as Chrysomya megacephala (Fabricius) are powerful evidence for estimating the death time of a corpse, but an established reference of developmental times for local blowfly species is required. We determined the developmental rates of C. megacephala from southwest China at seven constant temperatures (16–34°C). Isomegalen and isomorphen diagrams were constructed based on the larval length and time for each developmental event (first ecdysis, second ecdysis, wandering, pupariation, and eclosion), at each temperature. A thermal summation model was constructed by estimating the developmental threshold temperature D₀ and the thermal summation constant K. The thermal summation model indicated that, for complete development from egg hatching to eclosion, D₀ = 9.07 ± 0.54°C and K = 3991.07 ± 187.26 h °C. This reference can increase the accuracy of estimations of postmortem intervals in China by predicting the growth of C. megacephala.     

CT、MRI在弥漫性轴索损伤法医学鉴定中应用价值分析

目的探讨CT和MRI检查方法在弥漫性轴索损伤(diffuse axonal injury,DAI)法医学鉴定中的应用价值。方法收集26例CT和MRI影像资料齐全的DAI鉴定资料进行回顾性分析,比较CT和MRI两种方法对DAI病灶检出率的差异,分析DAI病灶检出数量与法医学鉴定结果之间的关系。结果 26例经MRI检出DAI病灶787个,经CT检出DAI病灶32个,MRI对DAI病灶的敏感度显著高于CT(P0.01)具有统计学意义。26例DAI鉴定的伤残等级数值与影像学检查发现的病灶数量之间存在负相关(r=-0.908,P0.01)。结论 MRI检查对DAI病灶的检出率较CT检查具有明显优势,可为DAI诊断提供更为准确的依据,在法医临床学鉴定中具有重要的应用价值。     

The Effect of Skin Debris on Gunshot Residue Sampling and Detection

These experiments were designed to determine whether skin debris (desquamated epithelial cells and apparent skin oils) affects gunshot residue (GSR) particle detection on the sticky tape lift samples prepared for scanning electron microscopy (SEM). A dabbing experiment showed that GSR particles accumulate not only on the adhesive surface of the sampler, but also on the epithelial cell surfaces. Samplers were loaded with target GSR followed by dabbing 30 times on the back of a hand. Backscatter electron images were taken at 20 kV and for some at 30 kV of the same areas. The samplers were then treated with a sodium/calcium hypochlorite solution (bleach) to remove skin debris and again imaged in the SEM. Comparison of these images shows more GSR particles will likely be revealed at 30 kV than 20 kV and more particles revealed by the bleach treatment in an automated SEM system.     

From papyrus to cyber: how technology has directed law enforcement policy and practice

Abstract

Cyber technology, both explicitly and implicitly, impacts every facet of local, state, national and international criminal justice operations. Unfortunately, technological changes, including cyber technologies, are rarely well thought out and may have unintended negative consequences. Additionally technology, and particularly cyber technology, evolves at a much faster pace than our understanding of the ethics, laws and policies involved. Consequently, citizens, criminals and justice professionals often rely on technology without the benefit of legal protections or explicit agency policy. This paper will examine how technology, both historically (non cyber) and contemporarily (cyber), has positively and negatively affected one aspect of the Criminal Justice enterprise – law enforcement.     

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) detection limits for blood on fabric: Orientation and coating uniformity effects

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to analyze four types of forensically relevant fabrics coated with varying dilutions of blood. The blood was applied in two manners, dip coating with a smooth and uniform layer and drip coating with droplets from pipettes. Spectra of neat and dip coated fabrics were acquired using controlled orientations, and these were compared to spectra collected on samples with random orientations. The improved reproducibility seen in visual inspection of the spectra is confirmed by principal component and linear discriminant projections of the spectra, as well as by statistical hypothesis testing. Principal component regression (PCR), using the regions of the IR spectra associated with the amide A/B, I, II, and III vibrational bands (3500–2800, 1650, 1540, and 1350 cm⁻¹), was employed on the more uniform dip coated spectra to estimate limits of detection for blood on two of the four fabrics – acrylic and nylon. These results demonstrate that detection limits for blood on fabrics can be decreased significantly by controlling for the orientation and face of the fabric samples while collecting spectra. Limits of detection for acrylic and nylon were found to be 196 × and 227 × diluted blood, respectively.     

The detection of clandestine graves in an arid environment using thermal imaging deployed from an unmanned aerial vehicle

The Middle East is one of the world regions that has frequently suffered from armed conflicts that resulted in mass burials. However, the detection of clandestine graves in such an arid environment by deploying remote sensing payload on unmanned aerial vehicles (UAVs) has received little attention. The present study used a UAV equipped with a thermal sensor aimed at narrowing down the search area of possible gravesites in the arid climate of Kuwait. The enclosed research area, which includes both control and experimental mass graves, was imaged for 18 months. The variation in topsoil temperature and soil moisture between the graves and their surroundings was evaluated. The results of the analysis demonstrated the effectiveness of thermal imaging techniques in detecting heat produced from buried sheep carcasses and detecting the change in grave soil moisture for our research environment for 7 and 10 months, respectively. The buried animals significantly influenced the topsoil temperature (p = 0.044), while the height from which the images were captured had an insignificant effect on the measured temperature within the range tested (p = 0.985). Furthermore, there was a negative correlation (−0.359) between grave temperature and the calculated soil moisture. The results from these cost- and time-effective search methods presented in this study confirm their potential for the detection of burial sites in an arid environment.     

Stability studies of ALD-52 and its homologue 1P-LSD

With the emergence of new psychoactive substances (NPSs) over the years, the substances detected on stamps (also known as blotter papers) have also evolved from the traditional drug—lysergic acid diethylamide (LSD) to the multiple variants of lysergamides such as ALD-52 and 1P-LSD. The analysis of such blotter papers is usually done by solvent extraction followed by identification using gas chromatography–mass spectrometry (GC-MS). This study has shown that hydrolysis to form LSD was observed in GC-MS analysis when ALD-52 was extracted with methanol. The extraction of ALD-52 using other solvents such as acetonitrile, ethanol, isopropyl alcohol, ethyl acetate, and acetone, followed by GC-MS analysis, was investigated. It is shown that alcoholic solvents such as methanol and ethanol will result in the conversion of ALD-52 to LSD during GC-MS analysis, whereas the sterically hindered isopropyl alcohol will prevent this conversion. Investigation also shows that the hydrolysis of ALD-52 to LSD occurs at the GC injector port. It was also observed that the degree of hydrolysis was more pronounced at a lower concentration (0.1 mg/mL). The study was extended to a close analog—1P-LSD, and the results showed that 1P-LSD similarly hydrolyzes to LSD. However, 1P-LSD was observed to be more stable than ALD-52 due to steric hindrance because of the propanoyl group.