25 Jan 2024

Is there a test for impairment due to drug use?

At a recent Employment Relations Authority hearing, expert witnesses were called to address the issue of whether the employee could be considered “under the influence” of cannabis following a specific test result.  This was for the purpose of interpreting the wording in the Collective Agreement during a disciplinary process. There was first a discussion about “under the influence” and “impairment” which are words that are commonly used in employment policies.  Here are some key points from the expert witnesses that employers may find helpful:



Many Drug and Alcohol policies refer to “under the influence of” or “impairment”.  One of the expert witnesses stated that it is widely accepted in safety critical/sensitive industries and workplaces that the aim of a drug testing program and policy is to reduce the potential for impairment from drugs and alcohol, and only a negative result can confidently exclude impairment.


You may like to review the wording of your policy to clarify that a non-negative drug test is considered potential serious misconduct.  If you adjust the wording in your policy, you need to consult with employees and consider their feedback before finalising your new policy, and you need to be able to demonstrate that all employees are aware of the new policy.


Give our People & Culture team a call if you need assistance in this area:  0800 383 737.


Meredith MacKenzie | People & Culture Specialist