SEM-EDS analysis and characterization of glitter and shimmer cosmetic particles

Perpetrators are often aware of commonly used trace evidence in forensic casework, thereby limiting potential transfer during a crime. With the lack of common evidence left behind at a crime scene, consideration of alternative potential evidence is necessary. Glitter and shimmer particles from cosmetic products will potentially transfer from or onto an offender, crime scene, or victim. The transfer of these cosmetic particles during a close personal attack generally goes unnoticed, and thus offenders are unaware of the use of such evidence that may associate a suspect to a crime scene. In this study, 36 glitter and 40 shimmer samples were analyzed using scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS) whereby characterization schemes were developed to help identify particles potentially transferred during close personal assaults. Samples were classified into 7 glitter and 4 shimmer groups based on elemental composition, and the developed classification models showed high potential to accurately associate or differentiate unknown cosmetic particles collected from a potential crime scene, with cross-validation accuracies ranging from 94 to 100%. Pearson results showed no overlap between inter- and intra-sample correlations, thereby suggesting low possibility of false sample identification. Analysis of variance with post-hoc Tukey test was subsequently performed to determine how well detected elements and element peak ratios differentiated the glitter and shimmer samples, respectively.