Marijuana urine tests flawed

‘An employee cannot be dismissed for being under the influence of dagga at work merely because a urine test detected traces of cannabis in his or her urine. Unless the employer can prove that the employee was under the influence of dagga while at work (something that cannot be done by using a urine test), it would normally not be legally permitted to dismiss that employee for substance abuse or for being under the influence of dagga at work.’ Professor Pierre de Vos – in an analysis of the recent ruling in Mthembu and Others v NCT Durban Wood Chips on his Constitutionally Speaking blog – argues that the CCMA got it wrong, primarily because it did not understand how cannabis testing works and what is being tested. In the case, the CCMA upheld the dismissal of several employees who tested positive for cannabis, based solely on the urine test. The applicants were dismissed because they were found guilty of being ‘under the influence of intoxicating substances while on duty’, something that created a risk for everyone at the company where dangerous machinery was being operated. De Vos says as the CCMA pointed out, a rule prohibiting employees from coming to work ‘hoog gerook’ on dagga would be no different from a rule prohibiting an employee from arriving at work ‘roaring drunk’. But he warns the comparison between alcohol and cannabis cannot be taken too far. While alcohol leaves the blood within a few hours after ingestion, traces of dagga stay in the body long after a person is no longer experiencing any effects from the dagga. Urine tests, he says, can detect dagga in the urine for about three to 30 days after use. ‘This means that it is more than likely that a person testing positive for having traces of cannabis in their system will not be under the influence of cannabis at all.’ The CCMA found that the ‘applicants were tested through a urine test and found to be under the influence of cannabis which was admitted by the applicants’. De Vos says this must be wrong, ‘as the test could not have found that the employees were under the influence of cannabis at the time of testing’. For this reason, he says, the dismissed employees were hard done by.

Mthembu and Others v NCT Durban Wood Chips

Full analysis on the Constitutionally Speaking blog