CBD or cannabidoil is the legal and non intoxicating derivative of marijuana.  It is used to treat pain, inflammation and other maladies including seizure disorders.  But some forensic tests confuse CBD with Tetrahydroacannabinol THC the intoxicating and federally restricted product. It is important to know whether a reported test for THC is correct or whether it can mistakenly report CBD as THC. 

From today's New Your Times:

The drug testing method in question involves a common chemical analysis device called a gas-chromatography mass-spectrometry, or GC-MS, machine. Most such devices require the drug testing lab to add a chemical to a sample in order to identify trace amounts of illicit compounds, in a process called derivatization. Labs can perform derivatization using a variety of chemical agents, but one of the most common is called trifluoroacetic anhydride, or TFAA.

 According to the 2012 journal article, TFAA when used by a GC-MS machine was unable to discern between CBD and THC. If a person who used only CBD were given a drug test that employed this device, method and chemical, the results would falsely report the presence of THC

https://www.nytimes.com/2019/10/15/science/cbd-thc-cannabis-cannabidiol.html?action=click&module=Well&pgtype=Homepage&section=Health