Oral Cavity Fluid as an Investigative Approach for Qualitative and Quantitative Evaluations of Drugs in Postmortem Subjects

: A relatively overlooked aspect of forensic science is the potential of oral cavity fluid for contributing to a forensic diagnosis. Although traditional specimens, like blood and urine, are routinely evaluated for forensic toxicology testing, fluid from the oral cavity has not been investigated as a matrix in postmortem cases. Our laboratory developed and validated qualitative and quantitative analytical methods for determining 47 medicinal and illicit drugs from oral cavity fluid. These developed methods aimed to compare results from liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analyses of oral cavity fluid to those of traditional matrices collected from the same postmortem subjects. Of 34 cadavers studied, 32 (including two decomposed and two drowned subjects) had detectable and quantifiable drugs in the oral cavity fluid and/or blood, urine, bile, vitreous fluid and/or liver tissue. The most significant finding was that 6-acetylmorphine (6-AM) was detected more frequently in oral cavity fluid (11 cases) than in blood and urine combined (6 cases). Compounds with a short window of detection, like the heroin metabolite, 6-AM and even heroin, could be detected more readily in oral cavity fluid than in urine. In 2017, the incidence of heroin-related overdose deaths increased to 15,958. Those data have shed light on the practicality of testing oral cavity fluid postmortem and its significance in forensic toxicology. In conclusion, this study showed that oral cavity fluid could be useful for detecting and quantifying drugs in postmortem subjects; moreover, oral cavity fluid may be particularly suitable when other matrices are limited or difficult to collect, due to body condition or putrefaction.