Quick Overview
- Police can demand a roadside breath sample without any suspicion at all, under a provision called Mandatory Alcohol Screening
- A “Fail” on the roadside device gives police what’s called reasonable grounds, enough to make an arrest and move to formal testing
- The right to a lawyer is temporarily suspended during roadside screening, but it kicks back in fully once someone is arrested
- A full evidentiary breath test happens at the station using an approved instrument, with strict rules around timing and calibration
- Refusing to provide a sample carries penalties just as serious as being convicted of impaired driving itself
- Recent Supreme Court decisions have tightened what counts as a valid roadside demand, including whether police actually have the device with them
Two Thresholds, Not One
An investigation like this doesn’t run on a single standard the whole way through. Two different thresholds come into play, and the gap between them matters more than people expect. Reasonable suspicion sits at the low end, just a reasonable possibility, nothing close to a probability yet. Courts weigh the whole picture here, an odour of alcohol, glossy or bloodshot eyes, slurred speech, admissions about drinking, driving that looked off before the stop even happened. No single detail decides it alone.
Reasonable grounds to believe sits much higher, closer to actual probability than mere possibility. This is the bar that has to be cleared before an arrest can happen, and in practice, it’s usually crossed the second someone registers a Fail on the roadside device.
No Suspicion Needed at All, Sometimes
Here’s where things get less intuitive. Since 2018, police have had a tool called Mandatory Alcohol Screening that sidesteps the suspicion requirement entirely. Any lawfully stopped driver can be asked for a roadside breath sample, full stop, no individualized suspicion of alcohol needed. A few conditions still have to hold. The stop itself needs to be lawful, the officer needs to actually have a screening device on hand, and the sample has to come immediately. Yes, this does infringe on Charter rights technically. Courts have upheld it anyway, reasoning the infringement is brief enough and the public safety interest weighty enough to justify it.
How the Sequence Actually Plays Out
A traffic stop kicks things off, sometimes for suspected impairment, sometimes for something as routine as a licence check. From there, an officer either forms suspicion or simply reaches for Mandatory Alcohol Screening, reads a formal demand, and runs the roadside device on the spot.
Three outcomes come out of that device. Pass, and things stop right there. Warn, generally between 50 and 79 milligrams of alcohol per 100 millilitres of blood, doesn’t clear the criminal threshold but still triggers a short provincial licence suspension. Fail is where things move fast, since that’s what hands police the grounds they need to arrest.
Arrest changes the entire posture of the interaction. Full Charter rights snap back into place at that point, and the driver has to be told why they’re under arrest along with their right to a lawyer, this time without delay. A second demand follows, requiring a trip to the station for breath samples into an approved instrument run by a trained technician. Drug suspicion adds another layer, a Drug Recognition Expert may step in to run a separate evaluation covering physical coordination, vital signs, and an eye exam.
The Lawyer Question, and Why It’s Confusing
People tend to assume the right to counsel applies the moment police get involved. It doesn’t, not fully, not at this stage. R. v. Thomsen and R. v. Orbanski carved out a specific exception for roadside screening, suspending that right temporarily. The logic behind it is fairly blunt: an ASD sample has to happen immediately, and arranging a private call with a lawyer on the shoulder of a highway in that same window just isn’t realistic. Courts accepted this as a justified, narrow limit on an otherwise core right.
The suspension has an expiry date built in though. Arrest following a Fail changes everything, and full legal counsel access has to be available before any further testing happens back at the station. It’s a detail that catches a lot of people off guard, and it’s exactly the kind of thing an Impaired Driving Lawyer Ottawa clients turn to will dig into when picking apart how an investigation unfolded..
Refusing Doesn’t Get Anyone Out of Trouble
A persistent myth floats around that refusing a breath test sidesteps the whole legal problem. It doesn’t. Refusal, whether at the roadside or at the station, stands as its own criminal offence, and the penalties are built to match, sometimes exceed, an actual impaired driving conviction. A first refusal carries a minimum $2,000 fine, which is actually steeper than the minimum fine attached to a basic over-80 charge.
The Courts Keep Tightening the Fine Print
Recent rulings have reshaped several of these procedural details. R. v. McColman shut down the idea that random sobriety stop powers extend onto private property once a vehicle leaves the public road. R. v. Breault tackled what “immediately” really means, ruling that a demand is invalid unless the officer actually has the device with them at the scene, no stalling while a colleague brings one over. R. v. Khandakar looked at the flip side, confirming that a driver who briefly refuses but changes their mind fast enough, while police could still lawfully take the sample, may not have committed the refusal offence at all.
Small details end up mattering a great deal because of rulings like these. Whether a device was physically present, how fast things moved, whether rights got explained at the right moment, any of it can shift whether a charge holds up.
Why the Procedure Itself Ends Up Being the Whole Case Sometimes
Constitutional weight sits behind every step here, and a misstep anywhere along the way, the wrong threshold applied too soon, a device that wasn’t really available, rights explained a beat too late, can affect whether the evidence collected afterward survives scrutiny in court. That’s really why bringing in Ottawa Impaired Driving Lawyers early tends to matter so much. Looking closely at how an investigation actually happened, not just what number showed up on the reading, is frequently where the real work of a case begins.
FAQs
Can the police make me take a breath test without any reason at all?
Yes. Under Mandatory Alcohol Screening, a lawfully stopped driver can be asked for a roadside sample without any individual suspicion needed first.
Do I have the right to call a lawyer during a roadside stop?
Not at that stage. The right is temporarily suspended during roadside screening, but it applies in full the moment an arrest happens.
Is refusing a breath test better than failing one?
No. Refusal is its own criminal offence, and the penalties can be even steeper than a basic impaired driving charge.
What happens if I fail the roadside test?
A Fail gives police reasonable grounds for arrest, which leads to a formal evidentiary breath test at the police station.
Does it matter if the officer didn’t actually have a breathalyzer on hand?
Yes. Recent Supreme Court rulings confirm a roadside demand isn’t valid unless the officer has the screening device with them at the time it’s made.
Summary
An impaired driving investigation in Ontario runs through clearly defined stages, starting with either reasonable suspicion or the broader Mandatory Alcohol Screening power, then climbing to reasonable grounds once a roadside Fail occurs. The right to counsel gets suspended briefly during roadside testing but comes back in full after arrest, and refusal carries its own serious penalties apart from an actual conviction. Recent Supreme Court and appellate rulings keep narrowing exactly what police need to do at each stage, which means the procedural details of an investigation can end up mattering as much as the test result itself.
This article is intended for general information purposes only and does not constitute legal advice. It does not create a lawyer-client relationship between LMS Lawyers and the reader. For advice specific to your situation, please consult a licensed lawyer.
