The random presence of glass and paint on the clothing and footwear of members of the general population: A US baseline survey at various seasons.

This study assists the interpretation of glass and paint evidence by filling an existing gap in the background occurrence that reflects the socioeconomic and demographic circumstances in the United States. The collection was performed in a college US city (Morgantown, West Virginia) to determine the effect of the type of clothing worn at different seasons on the presence of glass and paint. Tape lifts and sole scrapings (1038) were collected from 210 participants and up to six clothing and footwear areas per individual. Glass fragments were analyzed via polarized light microscopy (PLM), refractive index (RI), micro-X-Ray fluorescence (µXRF), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), while paint specimens were examined by light microscopy and infrared spectroscopy (µFTIR). Higher occurrences of glass and paint were found in the winter season. The winter collection yielded 10 glass fragments and 68 paint particles, whereas the summer collection resulted in one glass fragment and 23 paint particles. The percentage of individuals with traces varied between seasons; 7% of individuals in the winter and 0.9% in the summer had glass, whereas 36% of individuals in the winter and 19% in the summer bore paint. Lastly, when considering the overall garment and footwear areas, glass was detected in 1.4% of the winter set, compared to 0.2% in the summer collection; paint was found in 9.2% of the winter collection, whereas only 4.2% was found in the summer set. There were no instances where both glass and paint were detected on the clothing and footwear of the same individual.

The analysis of glass from portable electronic devices and glass accessories using µ-XRF for forensic investigations.

In this study, glass from 30 different portable electronic devices (PED) screens, 15 screen protectors (SP), and 3 brands of liquid glass (LG) were analyzed using a µ-XRF instrument equipped with two silicon drift detectors (SDD). Additional analysis of six fragments, all originating from the same PED and SP screen, assessed the elemental homogeneity within a single glass source. Examinations of the 30 PEDs and the majority of the SP screens revealed spectra with low sodium and high potassium, which is likely due to the ion exchange process at the surface during the glass manufacturing process. The absence of calcium in the XRF spectra was also characteristic of PED formulations. Initial spectral overlay examinations classified the PED and SP samples into major groups based on their distinctive elemental profiles (5 PED groups, 4 SP groups). Further discrimination of within-group samples was possible when considering reproducible differences in signal intensities (discrimination 98.4 % PED, 98.1 % SP). Additionally, a 3 s (3 % Relative Standard Deviation, RSD) comparison criterion produced the lowest false exclusion rates among same-source fragments (3.3 % PED, 0.8 % SP) while maintaining a high discrimination power among different-source fragments (98.4 % PED, 100 % SP). Same source PED and SP samples resulted in low variability within most elements examined (< 8 % RSD), except for potassium. An experimental threshold established from the quantitative metric of spectral similarity, spectral contrast angle (SCA) ratio of same-source and different-source datasets, produced false exclusion and false inclusion rates of 4 % or 0.95 % for PED and SP fragments, respectively. Spectra of just the liquid glass residues indicated some major elements present but the effect of these elements in PED fragments treated with liquid glass was not significant. This study provides a preliminary understanding of the elemental composition of modern PED glasses and their accessories and the discrimination capability of µ-XRF for forensic comparisons.