Tag: Duquenois-Levine

Drug Charge Dismissed After GRL Challenges Marijuana Identification

GRL recently put its knowledge of drug identification procedures to the test in a case involving alleged THC vape liquid. Police seized a vape cart during a traffic stop.  Field testing of the liquid extract showed a positive color change indicating the possible presence of marijuana. Frequent readers of the GRL Law blog know that field testing can mistake CBD for marijuana.  We’ve discussed this phenomenon here. This is where things get interesting. Police didn’t send the cart to the state crime lab.  Instead, they sent it to a local department that employs an officer with training in marijuana identification.  […]

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Problems with the Identification of CBD by Thin Layer Chromatography

Thin layer chromatography (TLC) is a well-known qualitative laboratory technique to separate, detect and identify plant material extracts that have been processed so they longer possess botanical characteristics that can be observed through macro and microscopic analysis.  This includes cannabis products like gummies, truffles, bars and other edibles, but also substances like tar, ground plant material and oils. In the FAQ section of the Iowa Division of Criminal Investigation Criminalistic Laboratory – Drug Identification website (https://dps.iowa.gov/divisions/criminal-investigation/criminalistics-laboratory/drug-identification), testing for controlled substances includes: The net weight (weight of substance without packaging) of the substance is recorded prior to any sampling and then […]

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Common Police Field Test Mistakes CBD for Marijuana

Police have historically relied on the Duquénois-Levine (D-L) colorimetric field test to presumptively identify botanical material as Cannabis for the purpose of arresting a suspect for possession of marijuana. The reagent used in the D-L test reacts with a particular part of the THC molecule producing an intense violet color that is readily identifiable by law enforcement at the roadside.  However, the D-L test is not specific for just THC.  Many other cannabinoids, including hemp-derived extracts such as CBD, will yield similar purple hues in the presence of the reagent. Of course, these extracts are not marijuana under Iowa law, but […]

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