A traffic stop can feel routine until an officer asks for a breath sample. In that moment, small details start to matter: what kind of test is being requested, how quickly it must be done, what happens if you hesitate, and what rights apply at that stage.
Impaired driving is still a major public safety issue, even as some national indicators trend downward. Statistics Canada reported 71,602 police-reported impaired driving incidents in 2023 (a rate of 179 per 100,000), while also noting 70 charges for impaired driving causing death and 532 for causing bodily harm that same year.
If you are trying to understand the process from the defence side, you will often hear a DUI & Impaired Driving Defence Lawyer in Toronto explain that impaired driving cases are won and lost on procedure, timing, and proof, not on assumptions. That is especially true when a file turns on what happened before any arrest was made.
Table of Contents
The Two Breath Tests People Mix Up
Most drivers think there is only one breathalyzer. In practice, there are usually two stages:
Roadside screening (Approved Screening Device)
This is the handheld test used at the roadside. It is meant to quickly screen for alcohol.
Evidentiary breath testing (at the station)
If the investigation escalates, you may be taken for evidentiary testing. These results often form the core of the Crown’s case.
The legal requirements and defence issues are different at each stage, which is why the first few minutes of the stop can become so important later.
Mandatory Alcohol Screening changed the first question police ask
Under Mandatory Alcohol Screening (often shortened to MAS), police can demand a roadside breath sample even without individualized suspicion, as long as the stop itself is lawful and the officer has the screening device available. That shift has changed how impaired driving investigations begin in many day to day stops.
In Ontario, the Ontario Provincial Police publicly announced that on certain OPP patrolled routes in the Greater Toronto Area, they would require a breath sample at every traffic stop as part of applying MAS more broadly.
The key point is that MAS does not eliminate legal limits. It changes the threshold for making the demand, not the conditions that make the demand valid.
A lawful demand is not just about what the officer suspects
From a defence perspective, one of the first questions is whether the demand was legally valid in the circumstances. That includes issues such as:
This is not academic. If a demand is legally invalid, the consequences can be significant.
Supreme Court Drew a Bright Line On Immediacy
A major case on this point is R. v. Breault (2023 SCC 9). The Supreme Court of Canada emphasized that when police order someone to provide a breath sample on an approved screening device, they must have immediate access to that device at the time the demand is made. In Breault, the demand was held invalid because officers did not have immediate access to an ASD when they demanded the sample.
The Court’s reasoning is practical and rights based. Roadside screening is treated as a brief detention where the usual right to consult counsel is delayed. That delay is only defensible when the screening happens right away. If the process stretches out because the device is not actually on hand, the legal justification starts to weaken.
What this means for real cases: timeline questions become evidence questions. Minutes matter, and notes, body worn video, dispatch logs, and testimony can all become relevant.
Refusal is its own charge, and it is treated seriously
Many people assume that refusing a breath test avoids evidence. In Canadian impaired driving law, refusal or failure to comply with a lawful demand can be charged as its own offence. The legal risk is that a refusal charge is often prosecuted with the same seriousness as an “over the limit” allegation.
Defences can exist, but they are fact driven. A common example is whether the demand was lawful in the first place, which is why issues like device availability and timing are so central after Breault.
What rights apply at the roadside
Drivers often ask two questions: “Do I have to answer questions?” and “Can I call a lawyer right now?”
At a high level:
This is why defence lawyers focus so closely on what happened, in what order, and how long each step took.
Practical steps that protect you without making things worse
Nothing below is a substitute for legal advice, but these are practical, non inflammatory steps that help preserve issues and reduce risk:
These steps are not about “beating the system.” They are about accuracy. Impaired driving cases often turn on whether procedures were followed and whether the evidence supports the charge beyond a reasonable doubt.
Why these cases can be defensible even when the allegation feels overwhelming
People are often surprised to learn how technical impaired driving litigation can be. A defence may focus on:
The goal is not to rely on one magic argument. It is to test the reliability and legality of the evidence at every stage, starting with the roadside moment.
The takeaway
Roadside breath testing is not just a single event. It is a sequence of legal steps, and Mandatory Alcohol Screening makes that sequence begin sooner and more often. At the same time, recent Supreme Court guidance reinforces that police powers at the roadside still come with strict conditions, especially around immediacy and device availability.
If you want, I can also draft a second, different blog topic for the same category (for example, drug impaired investigations and oral fluid screening, or how “care and control” differs from actual driving) while keeping the same tone and avoiding overlap with the site’s existing posts.
