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Presumption of BAC
Criminal Code of Canada
258 (1) (c)
Presumption of BAC
(c) where samples of the breath of the accused have been taken pursuant to a demand made under subsection 254(3), if
(i) [Repealed before coming into force, 2008, c. 20, s. 3]
(ii) each sample was taken as soon as practicable after the time when the offence was alleged to have been committed and, in the case of the first sample, not later than two hours after that time, with an interval of at least fifteen minutes between the times when the samples were taken,
(iii) each sample was received from the accused directly into an approved container or into an approved instrument operated by a qualified technician, and (iv) an analysis of each sample was made by means of an approved instrument operated by a qualified technician, evidence of the results of the analyses so made is conclusive proof that the concentration of alcohol in the accused's blood both at the time when the analyses were made and at the time when the offence was alleged to have been committed was, if the results of the analyses are the same, the concentration determined by the analyses and, if the results of the analyses are different, the lowest of the concentrations determined by the analyses, in the absence of evidence tending to show all of the following three things
that the approved instrument was malfunctioning or was operated improperly,
that the malfunction or improper operation resulted in the determination that the concentration of alcohol in the accused's blood exceeded 80 mg of alcohol in 100 mL of blood, and
that the concentration of alcohol in the accused's blood would not in fact have exceeded 80 mg of alcohol in 100 mL of blood at the time when the offence was alleged to have been committed;
Presumption that BAC at time of test is same as BAC at time of offence. This is probably the most litigated section in the Criminal Code of Canada. Issues include: "as soon as practicable", "not later than two hours", "interval of at least fifteen minutes", "received directly", "approved instrument", "qualified technician", and "evidence to the contrary". Since 2008 "evidence to the contrary" in the sense of contradiction of the machine by evidence of drinking scenario followed by a toxicological opinion is not a defence.
This short-cut is available to the Crown where the first breath test was taken as soon as practicable (and in any event within two hours) after the incident. If this evidentiary short-cut is not available to the Crown, e.g. first breath test was delayed outside two hours, then the Crown must call evidence from an expert witness, usually a toxicologist from the Centre of Forensic Sciences. If the Crown forgets or neglects to do the latter and the Court has a reasonable doubt about the first breath test being within two hours or as soon as practicable then the Crown cannot prove its case. This is one of the few reasons for acquittal remaining to persons accused with over 80.
The modern evidentiary breath testing equipment used in Ontario is designed with software that requires that the first two breath tests normally be spaced at least 17 minutes apart i.e. with an interval of 15 minutes. Subsequent subject tests or "stand-alone" (Esc Esc B) breath tests can, however, be performed at other intervals. Although it is not required in the Criminal Code, protocol dictates that the truncated results of the two tests must be within 20 mg/100 mls of each other. 3 digit test results (e.g. 123 mg/100 mls or .123) are rounded down to 120 mg /100 mls or .12. The rounded down results must be within 20 mg / 100 mls of each other (e.g. readings of 155/131 are acceptable but 151/129 are not).
Once established this presumption is extremely difficult to rebut. Please see the decision of the Supreme Court of Canada in R. v St-Onge Lamoureux noted below.