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Blood and serum specimens from 100 subjects in a driving study were tested for the presence of delta 9-tetrahydrocannabinol (THC) by 3H- and 125I-labeled RIA and GC/MS. The specimens were also analyzed for 11-nor-9-carboxy-delta 9-tetrahydrocannabinol by the two RIA methods. Blind quality control specimens containing THC were included with each batch of subject specimens and sent coded to three participating laboratories. The methods were assessed for accuracy, reproducibility, detectability, specificity, and the results correlated. It was found that serum was a better matrix than blood for determination of cannabinoids. The three methods gave parallel but significantly different quantitative results, apparently due to calibration problems. However, each technique was capable of measuring THC concentrations up to three hours after usage.

Comparison of glass particles by the forensic scientist is routinely accomplished by measuring some physical properties. Direct comparison of densities ϱ and refractive indexes (ͻC, ͻD, and ͻF being the refractive indexes determined at 6563, 5893, and 4861 nm, respectively) are the most widely used physical measurements because of convenience, reproducibility, sensitivity, and applicability to small sample size. Traditionally, if the physical comparison showed significant difference, it was concluded that the two glass samples could not have had a common origin. Conversely, when the specimens were not distinguishable the forensic scientist reported these samples as possibly having the same origin. Generally he did this without giving consideration to another variable-elemental composition of the samples.

The major psychoactive cannabinoid in marihuana, Δ9-tetrahydrocannabinol(THC) was measured in 1792 randomly selected blood specimens from erratic motorists arrested for impairment who submitted to blood alcohol sampling. Of these specimens, 14.4% were positive for THC (5.5 ng/mL). In those erratic driver specimens negative for alcohol THC positives rose to 23%. Drivers who used marihuana covered a broad age range. Aliquots of hemolyzed blood (10 μL) were analyzed by a sensitive radioimmunoassay (RIA) not requiring extraction. RIA accuracy and specificity were validated by gas liquid chromatography/mass spectroscopy (GLC/MS) split pair analysis (correlation coefficient = 0.93). This initial experience should facilitate and amplify a program designed to set forth the epidemiology of marihuana use in motorists and possible behavioral correlates.