The Dräger DrugTest 5000 has been approved as Canada's very first roadside saliva drug-screening test, but this German-made device is a far cry from an alcohol breathalyzer in one important respect: it doesn't actually measure impairment.

Instead, the DrugTest 5000 is supposed to determine the presence of THC during a roadside stop by police. (The device can also detect the presence of amphetamine, methamphetamine, cocaine, morphine, diazepam and methadone, according to a corporate flyer — but in Canada, it will only be used to test for the presence of THC and cocaine.)

Legally speaking, the results from the the DrugTest 5000 could serve as reasonable grounds for police to detain a driver for further testing. That testing would purportedly determine actual impairment by drugs, which would be a criminal offence, although the government's THC-blood-testing regime is scientifically flawed, as The Leaf News reported last year.

B.C. impaired-driving lawyer Kyla Lee has pointed out some of the potential flaws with the Dräger device. For starters, it only works properly in temperatures between 5 C and 40 C, which rules out much of Canada during the winter. On top of that, getting a result can take a long time — between five and 10 minutes, according to Dräger literature.

The device was also found to return a significant number of false positive results in a Norwegian study.

Regardless, the federal government will give $81 million to provincial and territorial police forces to purchase approved screening devices, such as the DrugTest 5000. Right now, no other devices have been approved.

In the end, though, fancy drug-testing devices like this aren't even necessary for police to get the reasonable grounds they need to demand a blood sample or perform an impairment evaluation by a trained officer. As a police official told the Winnipeg Free Press last week, police can already use an existing standardized field sobriety test to establish those grounds.

Why, then, is the Canadian government spending tens of millions of dollars on a device that will likely be challenged in court?

It might come down to political cover.

Remember, cannabis legalization is a gamble for the Liberal Party, and there's an election coming up. No government wants to be accused of going easy on impaired drivers, but providing police with a shiny new device to fight drug-impaired driving might help mitigate that political risk.