Impairment vs detection: the choice at the heart of your policy
Last verified:
There is no reliable roadside-style impairment test for THC. Every drug and alcohol policy therefore makes a choice — test for presence, manage for impairment, or blend both — and the defensibility of everything downstream depends on making that choice explicitly.
Option one: detection cut-offs
What it is: exceeding a named cut-off under a named standard is itself the breach. Why it survives: it is objective, consistently applicable, and has been upheld — Gauci v DP World is the clearest example, where the Commission accepted the policy set cut-offs rather than impairment measures, neutralising the “I wasn’t impaired” defence. The cost: it will catch lawfully prescribed, unimpaired workers, so it must be paired with a disclosure-and-assessment pathway or it manufactures discrimination risk and quiet concealment.
Option two: impairment-based
What it is: action turns on observable fitness for work — behaviour, incidents, supervisor observations — with testing as one input. Why choose it: fairest to a prescribed workforce and closest to the actual WHS risk. The cost: it demands trained supervisors, documented observation protocols and consistent application; done sloppily it collapses into subjective judgment calls that are easy to attack.
Option three: the deliberate hybrid (most common, most litigated)
Cut-offs for safety-critical duties; impairment-and-assessment management elsewhere; disclosure feeding a documented fitness-for-work process across both. The failure mode is the accidental hybrid — impairment language in the policy, cut-off enforcement in practice. Whichever blend you pick, the drafting must match the enforcement exactly, because the gap between them is what opposing lawyers read aloud.
The test your choice must pass
Could a supervisor, a tester and a tribunal each open your policy and give the same answer to: what is being measured, against what threshold, with what consequence, and what happens differently when the use is a disclosed prescription? If yes, you have a policy. If no, you have a future exhibit. The Policy Pack template drafts all three options with the blanks in the right places.