Forensic science international
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Delta9-Tetrahydrocannabinol (THC) and 11-nor-Delta9-tetrahydrocannabinol-9-carboxylic acid (THCA) are equally used to indicate consumption of cannabis (hashish and marijuana). Publications of the early 90's demonstrate the possibilities of determining THC, cannabinol (CBN), and cannabidiol (CBD). All these substances are present in cannabis smoke and can be incorporated into the hair only by contamination. ⋯ Thirteen were negative for THC and positive for THCA, and six were positive for THC but negative for THCA. The cases were selected by an ELISA test or re-examined when the blood/urine results or the statement of the accused did not match with a THC outcome. The most appropriate strategy to prove cannabis consumption is immunochemical initial test followed by a GC/MS/MS confirmation of THCA.