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Journal Article


Drasch G, von Meyer L, Raider G, Jagerhuber A. Blutalkohol 2003; 40(4): 269-286.


Institut fur Rechtsmedizin, D-80337 Munchen, Germany.


(Copyright © 2003, International Committee on Alcohol, Drugs and Traffic Safety and Bund gegen Alkohol und Drogen im Stra├čenverkehr, Publisher Steintor Verlag)






Data from 2001/2002 on 585 car drivers under the sole influence of cannabis who were conspicuous to the police (mostly during routine testing) were re-evaluated. It was tested, whether the deficiency symptoms as described by the police would serve as a guideline to establish a threshold value for absolute driving inability. For this purpose, possible parameters like THC concentration in serum and the Cannabis Influence Factor - CIF=([THC]+[THC-OH]) x 100/[THC-COOH]) (molar concentration as proposed by DALDRUP), were compared to the frequency of differing deficiency symptoms. Statistically significant results were obtained between both factors as well as the statements "concentration deficiencies", "continuously forgets something", "cannot follow longer sentences", "instructions must be repeated several times" and the two tests "finger to nose" and "standing on one leg". There was a continuous increase in the frequency of these deficiencies with the THC concentration in serum, with the exception of extremely high concentrations, at which point the frequency decreased again. This indicates that, in principle, it is possible to establish a toxicological defined threshold limit for the THC concentration. The level of this limit, however, cannot be deducted from our study. Moreover, as expected, the THC concentration decreases, as the time span between the incident and the blood sampling increases. In contrast to this the CIF was proved to be independent from this time span, at least within the first 120 minutes. With the CIF, the frequencies of the deficiencies are distributed in a different way than with THC concentration: At a CIF of 10 there is a distinct leap from low to high frequencies, while at higher CIF values a saturation leads to a plateau value for the frequencies. Forming a sum score for the six deficiencies, as described above, the optimum separation value between high and low frequency can be determined at a CIF of 10. It is therefore proposed to assume absolute driving inability by cannabis from a CIF of 10. If the CIF is not calculated from the molar concentrations but from the absolute concentrations, the analogue threshold limit is 9.

Keywords: Cannabis impaired driving


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