Volume 23, Issue 2 (April 1978)
A Study of False Positives in the Chemical Identification of Marihuana
Many authors have reported using the Duquenois, Duquenois-Negm, Duquenois-Levine, or modified Duquenois-Levine color tests on various substances with varying results. Some authors  apparently consider any resultant color to be a positive response. Recently this diversity of testing methods has been used by defense lawyers in an attempt to confuse judges and juries. Therefore, a search of the literature was conducted for the various substances reported to give a positive response to any of the above methods; all of those that were commercially available were tested with the modified Duquenois-Levine test and thin-layer chromatography (TLC) employed by this laboratory for marihuana identification. In addition, other compounds of similar structures were selected and tested in like manner, as were minor components of Cannabis resin . Another major objective was to determine if a mixture of materials that would lead to a false positive identification of marihuana could be made.