사례연구: 바이오마커(Uric acid 및 Coprostanol) 기반 생체 배설물의 법과학적 식별: 분석 프로토콜 및 사례 적용

This study selected uric acid and coprostanol as biomarkers of biological excreta and applied BSTFA (1% TMCS) derivatization followed by GC-MS analysis to two forensic casework submissions. To improve applicability to trace and localized evidence, we implemented analyte-specific sample preparation strategies and proposed a qualitative identification workflow incorporating retention time agreement with authentic standards, a selected-ion monitoring (SIM) ion set, ion ratios, an S/N criterion (S/N≥3), and procedural blank confirmation. In addition, because uric acid is poorly soluble, pretreatment and derivatization conditions were refined to enhance detection stability in trace swab specimens. In Case 1 (a cotton swab collected from a contaminated area on a vehicle windshield), uric acid was confirmed by comparison with an authentic standard using the characteristic ions (m/z 73, 441, and 456) of the uric acid- 4TMS derivative. In Case 2 (a localized contamination on the back area of men’s underwear), coprostanol was confirmed by comparison with an authentic standard using the characteristic ions (m/z 370, 355, and 215) of the coprostanol-1TMS derivative, and the concurrent detection of cholesterol suggested possible contamination containing human fecal components. These findings demonstrate that biomarker-targeted derivatization GC-MS can support source attribution of biological excreta contamination even in trace and localized specimens and provide baseline data for developing protocols applicable to forensic casework.