Characterization of Glitter Cosmetic Particles Using FT-IR Spectroscopy

With the common knowledge of DNA and fingerprints being used as trace evidence in casework, many perpetrators attempt to mitigate the transfer of such evidence at a crime scene. However, since close personal attacks are common, it is necessary to account for the potential lack of such evidence that may associate a suspect to a crime scene by considering other potential evidence. One type of evidence that is commonly overlooked by offenders is that of cosmetic transfer. Specifically, glitter components from cosmetic products may potentially transfer from or onto an offender, the crime scene, or the victim. In this study, 36 glitter samples were analyzed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR) in an attempt to develop a characterization scheme to aid in the identification of glitter particles that may transfer during personal assaults. Samples were separated into six classes based on chemical composition, and various statistical methods were used to determine the potential to classify glitter particles. Results of the developed scheme showed great accuracy, with at least 99% classification rates using three cross validation models. The developed classification model provides a basis for further identification of unknown glitter samples collected from a potential crime scene.