It became a controlled substance in 1914 under the Harrison Narcotic Act and was illegal even for doctors to prescribe in 1919.
These tests can show any controlled substance that has been used within a six month time period.
The recent jail sentence stems from El getting busted, once again, for possession of a controlled substance.
They then had her perform a field sobriety test, which she presumably failed as she was arrested under suspicion of being under the influence of a controlled substance.
Knight is currently charged with one count of misdemeanor battery and two felony counts of possession of a controlled substance.