Bill C-46 and Drug-Impaired Driving: Wacky Tabacky, Weird Science and the Law

This week’s blog focusses on Part 1 of Bill C-46, which amended provisions of the Criminal Code dealing with drug-impaired driving, and information about what constitutes drug-impaired driving.

As mentioned last week, you can find a full version of Bill C-46 at

Just as a friendly reminder, the content of this blog is provided for general information purposes only and does not constitute legal or other professional advice or an opinion of any kind.

Part 1 of Bill C-46, among other things, introduces the following amendments:

(a) enacts new criminal offences for driving with a blood drug concentration that is equal to or higher than the permitted concentration;

(b) authorizes the government to establish blood drug concentrations; and

(c) authorizes police officers who suspect that a driver has consumed drugs to demand that the driver provide a sample of a bodily substance for analysis by government-approved screening equipment.

With the imminent legalization of cannabis in Canada, it is important to acquaint yourself with the effect that a left-handed cigarette can have on your operation of a motor vehicle and amendments to the law around drug-impaired driving.


Drug per se levels

Part 1 of the Bill will create new drug per se level offences.

What this means is that the government will establish a hard limit for blood-drug concentrations (“BDC”), in relation to different drugs. So, if your BDC is recorded over this set limit (within two hours of operating a motor vehicle) then an offence occurs, independent of whether the drug had any effect on your ability to operate a motor vehicle.  This is similar to the “Over 80” offence in the Criminal Code, which criminalizes having a blood alcohol concentration of Over 80 mg of alcohol per 100 ml of blood.

Here are a few of the offences related to drug-impaired driving:

  1. Operating a motor vehicle while your ability to do so is impaired by any degree by alcohol or a drug or by combination of alcohol and drug – s. 320.14(1)(b)
  2. Having a blood drug concentration that is equal to or exceeds the per se limit – s. 320.14(c)

Who is going to set these per se limits for drugs? Bill Nye? Doc Brown?  Maybe Dr. Jekyll? Nope.  Parliament will establish the actual per se levels for drugs, including the per se limit for our little green friend Tetrahydrocannabinol (“THC”), the primary psychoactive compound in cannabis.


Weird Science: Determining a per se concentration for THC

The issue with establishing a per se concentration for THC arises from two things:

  1. What happens to THC once it enters your body; and
  2. How THC effects your body.

If you didn’t know, cannabis is commonly taken by smoking. When cannabis is smoked, THC is rapidly absorbed through your lungs and circulated throughout your body. This results in peak THC levels during the actual smoking of cannabis.  However, when you stop smoking, THC concentrations in your blood stream begin to rapidly decline by way of relocation into fatty tissues of the body.

Unlike cases involving the consumption of alcohol, the impairment effect from THC is not easily correlated with the actual concentration of THC in your blood. Maximum drug effects from THC may occur much later than peak blood concentrations of THC.

What this means is that an hour after smoking, when you’re listening to “Feelin Alright” by Joe Cocker, the THC levels in your blood stream may be quite low, but you may still be high as a kite.

Due to the lack of correlation between the timing of impairment effects of THC and THC blood drug concentration levels, it is difficult to set a per se limit that reliably reflects cannabis impairment.

If you’re looking to have a wild weekend and learn more about per se limits and some pharmacology, here are a few links:

Report of Drug per se Limits by the Canadian Society of Forensic Sciences Drugs and Driving Committee –

Estimating the Time of Last Cannabis Use from Plasma-Tetrahydrocannabinol and II-nor-9-Carboxy-Tetrahydrocannabinol Concentrations from the American Association for Clinical Chemistry –


The new Blood Drug Demand

Traditionally, during a drug-impaired driving investigation if a police officer has reasonable grounds to believe a driver is impaired by drugs, that police officer may demand that the driver submit to a Drug Recognition Expert (“DRE”) evaluation, pursuant to s. 254(3.1) of the Criminal Code. This calls for the driver to submit to a field sobriety test, which can be performed at the roadside.

If there is evidence of impairment, the driver will be taken to a police station for further evaluation of drug impairment by an officer trained in the DRE program. The evaluation at the station includes several hysterically reliable procedures to detect drug impairment, like pulse checks, blood pressure, body temperature, and finger-to-nose & balance tests.

Bill C-46 expands this demand.  Now, if the police officer has reasonable grounds to believe you were driving while impaired by a drug or that your BDC level exceeds the per se limit, the officer may demand that you provide a blood sample to determine your BDC.  Not intrusive whatsoever.

I know what you’re thinking…I’ll just pretend to be unconscious – that way I can’t consent to a blood sample. Bad news for you: the Government doesn’t need your consent.  But don’t fret, friends. We do not yet live in George Orwell’s “Oceania”, and no officers will be running around in lab coats pricking citizens with needles.  The new s.320.29 of the Criminal Code requires a warrant to be issued by a Justice before a blood sample can be collected.  A Justice may issue a warrant to obtain a blood sample from a person where they are satisfied of the following:

  1. There are reasonable grounds to believe that the person was involved in an accident causing bodily harm or death within the previous eight hours;
  2. There are reasonable grounds to suspect that there is alcohol or a drug in the person’s body; and
  3. A doctor is of the opinion that the person is incapable of consent and that the blood sample would not endanger the person’s health.


Once again, the question remains: How much invasion into our privacy are we willing to endure to potentially increase the safety of our roads? As the legalization of cannabis becomes a reality, changes to our country’s driving laws are necessary for the safety of the public. However, our understanding of drug-impaired driving is very much in its embryonic stage.  Parliament has acknowledged this by providing for a review of the new provisions in three years, which will hopefully allow for the provisions to grow alongside our understanding of drug impairment.


Further Information

If you or someone you know requires assistance with an impaired driving charge, contact Louis Luciani at or at (604) 669 – 5500.