Thank you very much.
Ladies and gentlemen, marijuana's THC does not impair a driver's blood; neither does alcohol, for that matter. Both of these substances impair a driver's brain, making the person unsafe to drive. We only test blood as a surrogate to try to learn what's in the brain. For alcohol, blood is an excellent surrogate. THC is not like alcohol. It's different biologically, chemically, and metabolically. For THC, blood is a terrible surrogate to learn what is in the brain.
Bill C-46 is based in part on the report from the Canadian Society of Forensic Science issued earlier this year. I largely concur with their findings, but I strongly disagree with their THC per se recommendations. I will confine my remarks to only that topic.
The two-tier structure in Bill C-46 perpetuates the myth that blood levels of THC correlate with levels of impairment, and they don't, as specified in the CSFS report itself. Drivers testing below five nanograms per millilitre of THC can be just as impaired as those testing above five nanograms. I submit that impaired drivers who kill or maim innocent victims and then test below five nanograms do not deserve protection from criminal prosecution.
Alcohol is unique among impairing drugs in that there is documented correlation between blood levels and impairment levels that simply does not exist for any other drug and has been shown to not exist at all for THC.
I point your attention to slide 1, which is before you right now. Much has been made of the fact that THC remains in the body for an extended period of time. It does not, however, remain in the blood very long at all. Since THC is fat-soluble, it is quickly removed from the blood as it is absorbed by the brain and other highly perfused fatty tissues in the body. The charts all demonstrate how rapidly THC is cleared from blood in both chronic and occasional users of marijuana.
Dr. Hartman's work, as shown in the two right-hand charts, showed that the peak level of THC declined an average of 73% within just the first 25 minutes after beginning to smoke a joint.
With a per se law, if you are above the limit, you are guilty of a per se violation, even if you can drive safely. Conversely, and this is something often overlooked, if you are below the limit, you are innocent of a per se violation even if you are seriously impaired. This latter point is the real problem with any THC per se quantitative level.
On slide 2 are frequency distribution histograms from four different forensic laboratories showing that the vast majority of cannabinoid-positive drivers arrested on suspicion of driving under the influence of drugs test below five nanograms. The largest of these studies showed that 70%, in more than 10,000 cases, tested below five nanograms. These drivers would not be criminally prosecuted under a five nanogram per se law.
There are two reasons for this phenomenon. First is the previously noted rapid depletion of THC from the blood. Second is the time required between arrest and taking a blood sample for testing.
This third chart superimposes the decline, shown earlier, of THC in blood on the elapsed time between dispatch of an officer to the scene of a crash and the time of taking a driver's blood in Colorado in 2013. What this chart shows you is that in the theoretical worst case, over one-half of cases of a driver smoking marijuana at the time of a crash, that driver would likely test below five nanograms, and that's for heavy users. For occasional users, the median level is just two nanograms. But wait. It gets worse.
In Colorado now, dollar sales of marijuana edibles exceed those of marijuana bud. Slide 4 shows THC levels found in blood on the left and in oral fluid on the right. Of users who consumed up to five times the standard 10 milligram THC dose of edibles, none of the subjects ever reached a five nanogram level in blood and very few even reached the two nanogram level. Drivers impaired by marijuana edibles would not be prosecuted under Bill C-46.
The relationship between blood alcohol level and impairment has been well established, perhaps most convincingly by the Borkenstein relative risk curve, shown on the left. As you have more alcohol in your blood, the chance of having a crash is increasing. By the way, this is only valid if alcohol is the only impairing substance in a driver's blood.
The largest similar study for THC was done by the European Union's DRUID project, which found no difference in propensity for crash risk based upon THC levels. Of greater utility, perhaps, are studies of physical impairment assessments versus blood THC levels.
Declues et al., in the right-hand chart of slide 5, found no relationship in “walk and turn”, “one leg stand”, or “finger to nose” assessments versus blood THC levels ranging between two and 30 nanograms per millilitre in whole blood.
Dr. Logan's study last year evaluated 15 different impairment assessments, none of which could distinguish between drivers testing above and those testing below five nanograms. Dr. Logan concluded, “A quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported.”
I submit further that to do so and to adopt Bill C-46 threatens to not only destroy credibility in the law but also to ensure that the majority of innocent victims of THC-impaired driving in Canada will not see the drivers who committed crimes upon their person brought to justice, and if that's not a crime, it should be.
We know that relying upon roadside impairment assessments alone is problematic. StatsCan figures bear that out. You have now seen that quantitative per se levels for THC also won't work. A combination called tandem per se, however, might be the answer.
Tandem per se requires a sequence of events to prove a driver guilty of driving under the influence of drug per se. Number one is that the driver was arrested by an officer who had probable cause, based upon the driver's demeanour, behaviour, and observable impairment, to believe that the driver was impaired. Number two is proof that the driver had any amount of an impairing substance in the driver's blood, breath, or oral fluid.
You can do better than what you currently have with Bill C-46. I hope you do.
I look forward to your questions.