Utility of caffeine analysis for forensic hair discrimination.

Utility of caffeine analysis for the purpose of forensic hair discrimination was evaluated. Methanol extracts of each 5-cm strand of scalp hair, after its incubation at 37 degrees C for 15 h, was analyzed by gas chromatography-mass spectrometry (GC-MS). For quantitative analysis of caffeine, caffeine-d3 was added as internal standard to the methanol extract. Hair specimens were obtained from three victims and from twenty-two volunteers. The results showed that caffeine levels in hair varied according to each individual; caffeine was detected up to a maximum level of 4.19 ng/5-cm hair. The concentrations of caffeine in hair obtained from four different regions of the scalp in twenty-two volunteers showed a coefficient of variation not greater than 24.7% for each individual. Based on our data, it was concluded that caffeine levels give relatively high reliability for discriminating a victim's hair from others at a criminal or accidental scene, although it should be used in combination with morphological examination and ABO blood group determination.