Examinations of Cosmetic Smudges Including Transesterification and Gas Chromatographic/Mass Spectrometric Analysis

Smeared traces of a cosmetic product may be transferred from a female victim to an assailant during crimes of violence. The procedure followed in the FBI Laboratory to characterize a cosmetic-like smudge is described, including extraction from a substrate, comparison with known specimens, and determination of the major inorganic and organic constituents used in the cosmetic formulation. A derivatization method used to transesterify oils and fatty acids commonly present in cosmetics is explained whereby the fatty substances are converted to methyl esters and subsequently identified by gas chromatography/mass spectrometry. This method is applicable to castor oil-based lipsticks as well as cosmetic powders, creams, and lotions that contain oils and fatty acids as main ingredients. Four examples are presented of forensic science evidence recently examined by the scheme of analysis set forth.