Automated Texture Recognition of Quartz Sand Grains for Forensic Applications*

Quartz sand surface texture analysis has been automated for the first time for forensic application. The derived Basic Image Features (BIFs) provide computer-generated texture recognition from preexisting data sets. The technique was applied to two distinct classification problems; first, the ability of the system to discriminate between (quartz) sand grains with upturned plate features (indicative of eolian, global sand sea environments) and grains that do not exhibit these features. A success rate of grain classification of 98.8% was achieved. Second, to test the ability of the computer recognition system to identify specific energy levels of formation of the upturned plate surface texture features. Such recognition ability has to date been beyond manual geological interpretation. The discrimination performance was enhanced to an exact classification success rate of 81%. The enhanced potential for routine forensic investigation of the provenance of common quartz sand is indicated.     

A Comparison of Four Presumptive Tests for the Detection of Blood on Dark Materials

Detection of blood on dark materials is difficult for crime scene examiners so presumptive tests are used to assist. This study compared the ability of luminol, leuko crystal violet, tetramethylbenzidine, and Combur Test®E to detect whole, diluted blood (1:100) and a key‐shaped blood transfer stain (1:10), on dark cotton sheeting, tea towel, socks, synthetic carpet, and car mats. Powdered bleach was used to evaluate specificity of the blood detection tests. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall misclassification rate (OMR) assessed the quality of the blood tests. Luminol was the preferred test for diluted blood having the highest sensitivity (79%–96%), NPV (66%–93%), and the lowest OMR (3%–15%). Luminol was also found to be most efficient with a testing time on 25 items of 2 h 50 min compared with up to 8 h. Overall, luminol was the most effective method, also providing information on bloodstain patterns.     

Quick Screening of Crystal Methamphetamine/Methyl Sulfone Exhibits by Raman Spectroscopy

Abstract: The analysis of mixtures of “crystal meth” (usually comprised of methyl sulfone [MS] and methamphetamine [MA]) by gas chromatography‐mass spectrometry (GCMS) is routine in many forensic drug laboratories. The utilization of Raman spectroscopy for the identification of such mixtures quickly and without the need for a separation technique is discussed. Samples were dissolved in water and Raman spectra of the resulting aqueous solutions were collected. By comparing these spectra to spectra of methylsulfone and MA mixtures of known composition, an indication of the composition of the sample can be obtained in only a few minutes. This spectral comparison also can be used as a semi‐quantitative analysis of MA concentrations in such exhibits.     

Enhancing the quality of aged latent fingerprints developed by superglue fuming: loss and replenishment of initiator

The recovery and identification of latent fingerprints from a crime scene are crucial to many investigations. The cyanoacrylate (superglue) fuming method (CFM), which develops fingerprints by growing a polymer coating over the print residue, is a powerful method but encounters severe limitations when prints are aged or exposed to harsh environmental conditions. We examine the aging process and how the changes that occur to a fingerprint residue over time influence the growth of polymer during development. We identify loss of initiator by erosion and degradation that, when coupled with a loss of water from the print residue, result in a decreased ability to polymerize ethylcyanoacrylate. Then, we present a methodology by which the ability of aged latent fingerprints to polymerize ethylcyanoacrylate is recovered. Two print enhancement agents, acetic acid and ammonia, are demonstrated to improve the growth of polymer from the print ridges by over an order of magnitude, while retaining the integrity of the print structure. Comparison between the two enhancement agents indicate that the enhancement occurs due to ridge coating by the ammonia or acetic acid and pH control of the latent print.     

Chemical composition and structure of the microcrystals formed between silver(I) and gamma-hydroxybutyric acid and gamma-hydroxyvaleric acid

This study examined microcrystals formed by silver with gamma-hydroxybutyric acid (GHB) and gamma-hydroxyvaleric acid (GHV), the five-carbon analog of GHB, in the presence of silver, copper, and lanthanide nitrates. Distinct microcrystals formed with silver (+1) and lanthanum (+3) ions but not with the copper (+2) ions. The crystals formed with GHB were distinctly different than those formed with GHV and in all cases, the drug microcrystals were easily distinguishable from reagent crystals. X-ray diffraction analysis provided definitive structure for the microcrystals. The morphological differences between the silver-GHB and silver-GHV crystals were characterized using simple measurements such as size and angles provided by image recognition software. The utility of the test for casework was demonstrated using spiked beverage samples.     

光谱成像检验技术

光谱成像组合了光谱技术和成像技术。通过运用成像光谱仪 ,光谱成像方法可以记录被检验物体在一个较宽光谱范围内均匀密集分布的窄波段反射光或荧光亮度分布影像 ,形成含有物体亮度信息和光谱信息的光谱影像集。这种技术方法可以用于物证的形态特征检验和物质成分检验。相对传统光谱检验或成像检验技术 ,光谱成像检验的能力和效果都具有明显优势。     

常见毒物的X射线衍射法检验

目的建立X射线衍射的检验方法为其在毒物分析领域的应用提供参考。方法使用X射线衍射仪对常见毒物进行定性分析。结果X射线衍射检验常见毒物快速而且准确。结论该方法具有很强的实用性。     

Determination of Changes in Crystal Violet and Phenoxyethanol (Dating Ink)

Ink dating is a significant problem in terms of forensic science. Ballpoint pens are generally used as writing tools on the documents. Aging is determination of the changes in dyes and solvents in the composition of ink over time by analytical methods. The evaporation of the solvents from the paper surface is faster than the decomposition process of the dyes. In this study, in 2017, we were asked by the court to determine whether the texts on the suspicious pages of an agenda dated 1996 were written within 2 years or earlier. Phenoxyethanol and dyes were examined in the composition of all suspected ink samples. The results show the determination of both the decomposition process of the dyes and the evaporation process of phenoxyethanol in the aging of the document entries written by ballpoint pen.     

X射线衍射法（XRD）检验无机炸药初探

目的建立XRD检验无机炸药成分的方法。方法利用X射线衍射仪对单体硝酸铵及其混合炸药、黑火药等进行检验分析。结果准确确定各炸药样品物质组成。结论该方法能够直接给出无机炸药中各组分的分子式,是无机炸药定性分析的理想的方法,并且操作快速简便,无损样品。     

Evaluation of the Photodegradation of Crystal Violet upon Light Exposure by Mass Spectrometric and Spectroscopic Methods

Abstract: Crystal violet is a very common dye in ballpoint ink. Recent research suggests that the degradation of triarylmethane dyes gives an indication of the age of a ballpoint pen entry on a document. The main problem for the quantitative evaluation of the degradation is that it is highly dependent on the exposure to light. Moreover additional factors, such as additives and substrate play an important role in this process. The aim of this work is to compare the degradation pathways of the pure dye in water and ethanol upon exposure to xenon light by UV/VIS spectrophotometry and laser desorption ionization. Significant differences have been observed in the products and the kinetics of the degradation. N-demethylation, an expected decomposition process, was found to take place only in aqueous solution and kinetics calculations showed that the degradation occurred 2.5 times faster in ethanol compared to water. The degradation of crystal violet in inks from four ballpoint pens on paper was also studied for entries made over 2–3 years. It was observed that degradation reactions were quenched by the presence of another dye due to competitive absorption. It was also observed that the thickness of a stroke (concentration of ink) influenced the degradation process. In the absence of light only one ballpoint pen showed slight degradation. A better understanding of the influence of the paper, ink composition, and storage conditions is necessary to interpret correctly the age of an ink based on the degradation of dyes.