Workplace drug and alcohol testing sits at the intersection of health and safety duties, employment law and privacy. Employers have a genuine interest in impairment, employees have privacy rights, and the case law has developed around the tension between them.
Testing is lawful. Testing without a properly developed policy, or testing in circumstances the policy does not cover, is where employers lose.
The health and safety basis
The duty to ensure health and safety so far as reasonably practicable provides the legitimate interest. Impairment is a hazard, and in safety-sensitive work it is a serious one.
That basis is strongest where the role is genuinely safety-sensitive — operating machinery or vehicles, working at height, handling hazardous substances, working around live electricity. It is weakest for roles where impairment creates no meaningful safety risk, and testing in those roles is much harder to justify.
When testing is generally accepted
Four circumstances are commonly provided for and generally supportable where the policy sets them out:
- Pre-employment, as a condition of an offer, where the role is safety-sensitive.
- Reasonable cause, where there is objective evidence of possible impairment — observed behaviour, not rumour or dislike.
- Post-incident, following an accident or near miss, where the policy sets the trigger clearly.
- Random testing, which is the most contested. It has been accepted for genuinely safety-sensitive roles, and is considerably harder to justify across a whole workforce indiscriminately.
Blanket random testing of employees in non-safety-sensitive roles has been found to be an unjustified intrusion. The narrower and better-reasoned the policy, the more likely it survives challenge.
The policy is the foundation
A policy that will hold up needs to be:
- Developed in genuine consultation with employees and any union. Imposing a testing policy without consultation is a good faith problem before it is anything else.
- Specific about which roles are covered and why they are safety-sensitive.
- Clear on triggers — what circumstances lead to a test, and who decides.
- Clear on the testing method and standards used.
- Explicit on consequences, including whether a positive result leads automatically to dismissal or to a process.
- Supportive as well as disciplinary, with a pathway for employees who disclose a problem before being tested.
- Communicated and acknowledged, with records showing employees received it.
Testing methodology matters
Method affects both reliability and defensibility. Recognised standards exist for workplace drug testing in New Zealand, and using an accredited provider following those standards is the practical baseline.
The distinction between presence and impairment is central and frequently misunderstood. Urine testing detects metabolites that can remain long after any impairing effect — particularly for cannabis. A positive urine test is not evidence that the person was impaired at work.
That gap is where dismissals are successfully challenged. Employers relying on presence testing should be clear in the policy that the standard is presence rather than impairment, and be prepared to justify why that standard is reasonable for the role. Oral fluid testing correlates more closely with recent use.
Confirmatory laboratory testing of any non-negative screening result is essential before any action is taken.
Process after a positive result
A positive test does not permit summary dismissal without process. The ordinary requirements of substantive justification and procedural fairness apply:
- Put the result and the allegation to the employee specifically.
- Provide the test documentation you are relying on.
- Allow representation and adequate time to respond.
- Consider the response genuinely, including any explanation such as prescribed medication.
- Consider alternatives to dismissal where the policy or circumstances allow.
Prescription medication is a recurring complication. Employees taking lawfully prescribed medication that could impair have an interest in disclosing it, and the policy should provide a confidential route for doing so.
Privacy
Test results are health information and personal information under the Privacy Act 2020. Collect only what is necessary, store securely, restrict access to those who genuinely need it, and retain no longer than required. Employees have access rights to information held about them.
Practical guidance
Employers should have a policy before they have an incident, because developing one in response to a specific employee is both procedurally weak and obviously targeted. Review existing policies against current case law, since this area has developed and older policies frequently overreach.
WorkSafe publishes guidance on impairment at work, Employment New Zealand publishes material on workplace policies and disciplinary process, and the Office of the Privacy Commissioner publishes guidance on health information. All are free.
General information only, not legal advice. Take advice before implementing testing or acting on a result.
