Governments in Canada take a hard line on impaired driving. The offence of “at or over 80” sets the legal blood alcohol concentration (BAC) at 0.08% (80 mg in 100 mL). The law and the police that enforce it rely heavily on breathalyzer results in prosecutions and roadside punishment of drivers. But beneath the veneer of technological certainty lies a troubling scientific reality: the accuracy of breathalyzers is fundamentally flawed due to the inherent variability of the partition ratio, the assumed relationship between breath alcohol concentration (BrAC) and BAC. This variability raises serious concerns about the fairness of at-or-over 80 DUI convictions Canada wide and Immediate Roadside Prohibitions (IRPs) in British Columbia where individuals may be penalized despite not actually exceeding the legal limit.
For insights on the latest advancements and challenges in impaired driving law, explore our article on the “Newest Developments in Impaired Driving Law in Canada.”
Breathalyzers, both the sophisticated devices used in criminal prosecutions and the handheld units employed roadside, operate on the principle that the amount of alcohol detected in a person’s breath directly correlates to the amount of alcohol in their blood. This correlation is expressed as a ratio, programmed into the breathalyzers at 2100:1, meaning one part of alcohol in the breath corresponds to 2100 parts in the blood. This standard ratio, however, represents an average, failing to account for the significant individual variations that exist within the population.
Winning or losing the “Average” lottery
Scientific research consistently demonstrates that the actual partition ratio can range from 1555:1 to 3005:1, influenced by factors such as:
• Body Composition: Differences in body fat and water content affect how alcohol is absorbed and distributed.
• Temperature: Even slight variations in body temperature can influence the volatility of alcohol and how much is released into the breath.
• Metabolic Rate: The speed at which an individual metabolizes alcohol impacts the relationship between BAC and BrAC.
This is a non-exhaustive list because there is an overall lack of study into the science of partition rations. Nevertheless, what we know about this variability has profound consequences for the legal system and anyone facing a DUI. Imagine two individuals who have consumed the same amount of alcohol, but have different partition ratios. Person A, with a ratio of 1700:1, may blow over the legal limit on a breathalyzer, even if their actual BAC is below 0.08%. Conversely, Person B, with a ratio of 2400:1, might test below the limit despite having a BAC above 0.08%.
The science behind breathalyzer inaccuracies is further explored in “How to Pass a Breathalyzer: What You Need to Know About Accuracy and Misconceptions.”
Implications for Criminal Prosecutions
In the context of criminal prosecutions, where breathalyzer results are presented as definitive evidence of guilt, this variability raises the alarming likelihood of wrongful convictions. Prior to 2008, individuals could challenge breathalyzer results by presenting evidence of their own partition ratio, or their drinking pattern leading up to arrest but this defence, known as “evidence to the contrary,” was abolished under Prime Minister Harper. While the change aimed to streamline legal proceedings, it has effectively silenced a crucial scientific argument that could safeguard against the conviction of innocent people.
Partition ratio and IRPs
For Immediate Roadside Prohibitions (IRPs) in BC, where the burden of proof falls on the driver to challenge a “Fail” result from a handheld breathalyzer, the variability of the partition ratio poses a significant hurdle. While drivers can still introduce evidence to the contrary, including arguments based on partition ratio uncertainty, persuading the tribunal of the scientific validity of this evidence is a huge hurdle.
Learn more about navigating BC’s Immediate Roadside Prohibition scheme in our guide “IRP Blog: Navigating the Traps of BC’s Immediate Roadside Prohibition Scheme.”
The challenge lies in the persistent gap between evolving scientific understanding and established myths. The RCMP give presentations to the tribunal about their belief in the accuracy and reliability of breath testing methods, further complicating the task of challenging breathalyzer results. And entire system is built upon this myth and it seems none are willing to confront the truth and see their understanding of breath tests fall apart.
The simplified “Fail” reading from handheld devices used for IRPs further obscures the nuances of potential inaccuracies stemming from individual partition ratios. This lack of detailed information makes it difficult for drivers to articulate a compelling argument against the seemingly straightforward breathalyzer result. Simply put, a “Fail” is easy for an adjudicator or a judge to understand. That we punish people based on an average that may not apply to the person is more difficult for adjudicators and judges to wrap their minds around.
The nuances of IRPs and their implications are discussed in-depth in “What happens when I file an Immediate Roadside Prohibition (aka an IRP) in dispute?”
The consequences of relying on a flawed system are far-reaching. Wrongful convictions in criminal cases harm people and erode public trust in the justice system, while inaccurate IRPs can lead to undue penalties, including license suspensions, vehicle impoundment, and significant financial burdens.
If Canada was to do things right, we would implement a more nuanced and scientifically sound approach to DUI enforcement. This could involve:
• Investing in research to develop more precise and individualized methods for assessing alcohol impairment. This could involve exploring alternative testing methods or refining existing technologies to incorporate individual-specific factors.
• Educating legal professionals and tribunals on the limitations of breathalyzer technology and the significance of partition ratio variability. A greater understanding of the science can lead to more informed decisions and a fairer evaluation of evidence presented by drivers.
• Reconsidering the abolition of the “evidence to the contrary” defence in criminal cases. Allowing individuals to present evidence of their own partition ratio could help safeguard against wrongful convictions.
One can reasonably imagine that some prosecutors are uncomfortable prosecuting at or over .08 case and if they’re not, they should be. Prosecutors have an obligation to see that injustice is not done and the current version of the Criminal Code banning the defence of evidence to the contrary ensure that some innocent people will be convicted, particularly if their breath test readings put them near the line.
When it comes to IRPs, the tribunal has a history of giving breath reading of Fail an advantage over all the evidence presented to show why the readings should be rejected. Recently, however, the BC Court of Appeal reminded them of the words of the legislation which grant no such advantage to the readings. Our hope is that evidence to the contrary is properly considered henceforth bearing in mind the frailties of relying on an average to punish people who may lose the partition ratio lottery by blowing “Fail.”
If you have been charged with a driving offence, DUI or refusal to blow anywhere in BC or the Yukon, you have found the right lawyers to help you with your case. If you have received an IRP, not that Kyla Lee of our firm wrote the textbook Immediate Roadside Prohibitions in Western Canada and she is the go-to resource in defending DUI driving prohibitions.
Call us or text us right away at 604-685-8889. We would be happy to help you protect your reputation, record and driving privileges.
If you’re seeking detailed strategies to protect your license following a DUI charge, check out “Caught for DUI in BC? Here’s How to Protect Your Future and Reputation.”