While we are on the issue of drug testing, the Supreme Court of Canada has come out with a very important decision dealing with evidence to the contrary in impaired driving cases, R. v. Gibson, 2008 SCC 16.

The case deals with straddle evidence and a rebuttable presumption on blood alcohol levels. As a former pharmacology grad student I have often watched in frustration as defendant’s experts give evidence that would not pass muster in an undergrad lab course, since a dui attorney could always be helpful in these cases. This decision is somewhat of a relief because it sets straight the meaning and utility of post consumption testing for elimination rates. These concepts are important to anyone administering a drug and alcohol discipline program, running grievances or doing human rights work in this area. They are well beyond the scope of a simple post.

Having said that, Madam Justice Charron states the following:

[3] As I will explain, it is my view that in all cases straddle evidence merely constitutes an attempt to defeat the statutory presumption itself and, as such, does not tend to show that the accused’s blood alcohol concentration did not exceed the legal limit at the time of the alleged offence within the meaning of s. 258(1)(d.1). I also conclude, on the basis of the undisputed scientific fact that absorption and elimination rates vary continuously, that post-offence testing of the accused’s own elimination rate

will rarely, if ever, add anything of value to the expert opinion evidence and, for obvious policy reasons, should not be encouraged, let alone required. You can check for the guidelines of the felony DUi in Texas and everywhere around depending o your location.

[4] It is undisputed that the human body absorbs and eliminates alcohol over time, and that absorption and elimination rates vary, not only from person to person, but also from time to time for the same individual, depending on a number of factors, some of which concern the person’s digestive process at the relevant time. It is therefore impossible to ascertain the precise rate at which the accused was metabolizing alcohol at the time of the alleged offence, although for people that is caught for reckless driving they can get help with these offenses from different sites online such as
https://www.duila.com/reckless-driving/. Parliament can be assumed to have known that blood alcohol levels are subject to these inherent variations. Yet, it saw fit to implement the presumption. The legislative scheme must be interpreted in this context.

[5] Because absorption and elimination rates continually vary, it is readily apparent that a breathalyzer reading of 95 mg, for example, may not reflect the actual concentration of alcohol in the accused’s blood at the time of the alleged offence — it would depend on the rate at which the particular accused is metabolizing the alcohol during the relevant time period on the day in question. Yet, it can be no defense for an accused to say that the actual alcohol concentration at the material time may have been less than the legal limit based on this variable alone. To admit such a defense would obviously fly in the face of the presumption itself. It is because of these inherent variations in absorption and elimination rates that the presumption of identity is needed in the first place. In order to facilitate proof of the offence, the presumption treats all persons as one person with a fixed rate of elimination and absorption.