South Australia Police have often been called Australia’s ‘fun police’ for their notoriously harsh stance on cannabis, but this week, they’ve outdone themselves with a bizarre ad designed to scare stoners.
The ad, which features a man haunted by smoke, is narrated by a ridiculously husky voice makes the claim that cannabis stays in your body for 24 hours after smoking.
However, SA police may have misjudged that one, as their 24-hour figure is not supported by any evidence. As a Magistrate David Heilpern noted last year, unscientific police guidelines lead cannabis smokers into a false sense of security. Magistrate Heilpern oversaw a case where a man followed police guidelines and avoided driving for 12 hours after smoking. Two days later, he was charged with drug driving.
How could that happen? Maybe it has something to do with the research South Australia Police apparently didn’t look at before picking up the camera.

The truth is, traces of cannabis’s psychoactive component THC can be found in your body weeks after you smoke. How long it remains there depends on several factors. Factors which the South Australia police have failed to mention. Such as your age, gender, metabolism, genetics and (obviously) the dose of the cannabis you consumed.
There are also many other things the ad left out. Firstly, they neglected to mention that testing for THC is dependent on THC actually being the part of cannabis that makes you high, which recent research has justifiably questioned.
Secondly, the ad might sound conclusive, but the amount of THC in your blood doesn’t necessarily tell us how high you are. Somewhere around the 20-hour mark, the pharmacologic activity of THC decreases by 50% as it is broken down by the body. At that point, it’s unlikely you’ll feel any impairment from the cannabis. And yet, you’ll test positive for both blood and urine tests.
South Australia police do not care if you’re impaired by cannabis. But rather, scaring users with convictions and misinformation.
According to the US National Drug Court Institute, traces of THC are detectable for an average of 2 – 7 days in blood, and between 3 and 67 days in urine. This means that someone who hasn’t smoked pot for 55 days might have the same amount of THC in their urine as someone who put their bong down to do the breathalyzer test. Now that’s scary.
At least Police are effective at catching drug-impaired drivers, right? Wrong.
Most tests conducted on Australian drivers aren’t even blood or urine tests. Instead, they are saliva tests. Saliva tests are one of the least effective forms of testing for cannabis – short of seeing if you ‘look’ high. These tests look for delta-9 THC, which sometimes can be found for an average of 24 to 48 hours, and sometimes up to 48 hours. However, ‘sometimes’ literal, as saliva tests are ineffective 16% of the time. Some people say you can beat them by drinking water, eating fatty foods, and using mouthwash – allowing impaired drug drivers to go free.
That brings us to this question. Should police be spending their money developing another creepy, dimly lit, unscientific ad, or is it time for new protocols that actually keep Australians safe?
Apparently, Professor McGregor agrees, as he told the ABC:
You can have someone with THC in their saliva who is not intoxicated. We need far better tests to go after impairment.
To the South Australia police force and their PR team – we’re not angry, we’re just disappointed. Get your act together.
For some real advice on driving and cannabis, see our guide here.