Saliva testing in cannabis impaired driving cases

Saliva sample tests do not indicate a blood THC level and are often used to extract admissions from those under investigation for cannabis impaired DUI charges in Ontario.

Police in Ontario are now starting to use saliva samples to test for the presence of cannabis/THC and other drugs when conducting DUI investigations. Saliva tests are not nearly as accurate as breathalyzers and do not give a blood THC level reading (just positive or negative). They are also not necessarily accurate or reliable. This being said they are used as an investigative tool as they indicate a person may have recently smoked or ingested cannabis (along with some other forms of drugs). This does not mean that the person is actually impaired or has a particular blood THC level.

Similar to a urine sample, a saliva test is only indicative of past use and not current impairment.

The test may be used by the police to coerce the driver into admitting what they smoked/took, perhaps foolishly believing that the test would show this anyway.

Unlike with alcohol BAC level, the police cannot test a THC blood concentration level with a saliva test and often use it as part of their evidence in combination with the statements obtained from the accused (if they talk and admit to it). The police may also use a positive saliva test to justify reasonable grounds to proceed with more invasive and accurate blood testing by consent or after obtaining a warrant/telewarrant.

When a person, who perhaps is under the influence, gets pulled over and submits a positive saliva sample they may feel it is in their best interest to explain its result. Their explanation may be that they “only had a couple hits” or that it is residual from previous use, but such statements will only hurt their case. Often they are talking themselves into being charged.

Even if their blood THC level is not obtained or proven they can still be convicted if the court believes they were impaired under CC s. 320.14(1).

By admitting to taking a couple hits, or whatever else, they are providing evidence of drug use which combined with DRE and roadside testing impairment evidence may be enough for a conviction.

Sometimes the admissions are made prior to the saliva sample being taken and used even if the saliva sample comes back negative. It is thus being used as an investigative tool which, similar to a lie detector test, can help extract confessions and admissions from the accused that are needed to press charges and obtain a conviction in court.

Whether the police have enough evidence to secure a conviction in court is up to the judge, but generally the Crown will need to present more evidence than just a saliva test result.


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