Driving Under the Influence of Legal Prescription Medication in Ontario

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Driving while impaired by lawfully prescribed medication is prosecuted in Canada under section 320.14(1)(a) of the Criminal Code, the same paragraph that covers alcohol and street drugs. It makes it an offence to operate a conveyance while your ability to operate it is impaired to any degree by alcohol or a drug. The word Parliament used is a drug. Not an illegal drug, not a controlled drug, and not a drug somebody else was prescribed. A pharmacy label explains why the medication was in your system on the night in question. It does not answer the charge.

By Fadi Matthew Kazandji, Founding Partner, Kazandji Law. Updated July 2026.

"But I had a prescription." Does that change anything under section 320.14?

Not to the charge itself. Section 320.14(1)(a) says a person commits an offence who operates a conveyance while the person's ability to operate it is impaired to any degree by alcohol or a drug or by a combination of alcohol and a drug. There is no qualifier anywhere in that paragraph for legality, for prescription status, or for whether you can buy the thing off a shelf at a pharmacy.

Now go one section back and look at the definitions. Section 320.11 defines the terms Parliament thought needed defining for this part of the Code: analyst, approved container, approved drug screening equipment, approved instrument, approved screening device, conveyance, evaluating officer, operate, qualified medical practitioner, qualified technician and vessel. Read the list twice. The word drug is not on it.

That absence is deliberate and it is the reason this whole area of law works the way it does. Parliament left the word at large. There is no statutory carve out for a valid prescription, because the offence is not about where the substance came from. It is about what the substance did to your ability to drive.

The only exceptions written into section 320.14 are in subsections (5), (6) and (7), and every one of them is about consuming a substance after you stopped driving. Subsection (6) protects a person who consumed the drug after ceasing to operate the conveyance and who then had no reasonable expectation of being required to provide a sample. That is a post driving exception. It has nothing to do with holding a prescription.

Ontario says the same thing in plainer language. The Ministry of Transportation states that impaired driving means driving when compromised to any degree by drugs, and it lists over the counter drugs and prescription medication alongside cannabis and illegal substances.

"I was not high. I was just drowsy." Why any degree of impairment is enough

Clients say this expecting it to help. It usually does the opposite, because drowsiness is impairment.

In R v Stellato, [1994] 2 SCR 478, the Supreme Court of Canada settled the standard. Impairment is a question of fact for the trial judge, and where the evidence establishes any degree of impairment ranging from slight to great, the offence is made out. The Crown does not have to prove that you were falling over, or that your driving was a marked departure from normal. Slight is enough.

So the fight is not about degree. It is about two other things.

The first is whether the impairment was of your ability to operate the conveyance, rather than of how you looked or sounded at the roadside. Red eyes, slow speech and a flat affect describe a person. They do not, on their own, describe a driver. The link has to be made out on the evidence, and the driving pattern the officer actually observed is usually the most important part of that evidence, whether it helps or hurts.

The second is whether the medication caused what the officer saw. Fatigue at the end of a night shift, a head cold, anxiety at being stopped by police, an old knee injury, a language barrier, and a medical condition that affects balance can each produce the same observations that get written into a set of officer notes as signs of drug impairment. Where an alternative explanation is available and the disclosure does not exclude it, the Crown has a problem with causation even if the observations themselves are accepted.

"I blew zero on the roadside screener." How a drug investigation starts where an alcohol one ends

A zero reading on an approved screening device tells the officer one thing: there is no meaningful alcohol in your breath. It does not end the stop, and in a prescription medication case it is often the moment the investigation changes direction rather than the moment it stops.

Section 320.27(1) is the provision that governs the roadside. Where an officer has reasonable grounds to suspect that a person has alcohol or a drug in their body and that the person operated a conveyance within the preceding three hours, the officer may demand any of three things: the physical coordination tests prescribed by regulation, a breath sample into an approved screening device, or a sample of a bodily substance to be analysed by approved drug screening equipment.

Note the standard. Reasonable grounds to suspect, which is a low bar, and much lower than the belief standard that comes later. Note also that the three demands sit side by side. The alcohol screening result does not have to come back positive before the officer turns to the drug side of the section.

The oral fluid screening equipment in paragraph (c) matters far more in cannabis and street drug investigations than in prescription medication files, and we deal with it in detail on our page about drug related DUI charges. In a medication case the officer far more often reaches for the physical coordination tests in paragraph (a), which is where the next section starts.

"There were only three tests at the roadside." What those three tests actually measure

Three is the correct number, and it is set by regulation rather than by the officer. Section 2 of the Evaluation of Impaired Operation (Drugs and Alcohol) Regulations, SOR/2008-196, prescribes exactly three physical coordination tests for the purposes of a roadside demand:

• The horizontal gaze nystagmus test. The officer moves a stimulus, usually a pen or a fingertip, across your field of vision and watches your eyes track it, looking for involuntary jerking as the eye moves toward the outside.
• The walk-and-turn test. You take a set number of heel to toe steps along a real or imaginary line, turn in a prescribed way, and walk back, while holding a starting position through a long set of instructions.
• The one-leg stand test. You raise one foot a set distance off the ground and count aloud until told to stop, while the officer watches for swaying, hopping, or putting the foot down.

Two of the three are divided attention tasks. They are not really tests of balance. They ask you to follow a long verbal instruction, hold a physical position, and perform a counting task at the same time, on the theory that a person whose attention is impaired will drop one of the three.

That design is why the conditions at the roadside are part of the evidence rather than background detail. The surface, the slope, the weather, the lighting, passing traffic, footwear, an old injury, body weight, age, and simple fear all bear on performance. So does the way the instructions were given, since a test that depends on following instructions is only meaningful if the instructions were delivered the way the officer was trained to deliver them.

None of that is an argument that the tests are worthless. It is an argument about the record. What matters in a courtroom is what the officer wrote down, when it was written, how much of it is standardised language repeated from file to file, and whether the notes let anyone reconstruct what actually happened on the shoulder of that road. Where the notes are thin, the weight of the result falls accordingly.

One practical point clients are rarely told. Performing poorly on these tests triggers an immediate provincial consequence in Ontario, separate from anything a court does later, and it applies whether the suspected substance is alcohol or a drug. On a first occasion the Ministry of Transportation imposes a seven day licence suspension, an eight hour education course and a $250 penalty, with escalating consequences on later occasions. That suspension comes from section 48.0.1 of the Highway Traffic Act, which sets seven days on a first suspension, 14 days on a second and 30 days on a third or later one.

"A different officer examined me at the station." Who the evaluating officer is

That second officer is not simply a colleague with a clipboard. The Criminal Code creates a specific role, and the qualification for it comes from a regulation.

Section 320.28(2) is the gateway. Where an officer has reasonable grounds to believe that a person operated a conveyance while impaired by a drug, or by a combination of alcohol and a drug, or committed an offence under section 320.14(1)(c), (1)(d) or (4), the officer may demand that the person submit as soon as practicable to an evaluation conducted by an evaluating officer, and may also demand samples of blood.

Look at the standard again. Section 320.27 at the roadside runs on suspicion. Section 320.28 runs on belief. That is a genuine escalation, and the grounds for it have to exist at the moment the demand is made, not be assembled afterwards out of what the evaluation eventually found.

Section 320.11 defines an evaluating officer as a peace officer who has the qualifications prescribed by regulation that are required in order to act as an evaluating officer. Section 1 of SOR/2008-196 supplies those qualifications in a single sentence: an evaluating officer must be a certified drug recognition expert accredited by the International Association of Chiefs of Police.

"They said the evaluation proved I was on opioids." What the evaluation can and cannot establish

The evaluation is a prescribed sequence, and knowing what is in it removes most of its mystique. Section 3 of SOR/2008-196 sets out the steps in order:

• a preliminary examination, taking the pulse and checking that the pupils are the same size and that the eyes track an object equally;
• eye examinations for horizontal gaze nystagmus, vertical gaze nystagmus and lack of convergence;
• divided attention tests: the Romberg balance test, the walk-and-turn, the one-leg stand and finger to nose with the head tilted back and the eyes closed;
• measurement of blood pressure, temperature and pulse;
• examination of pupil size under low ambient light, near total darkness and direct light, plus examination of the nasal and oral cavities;
• a check of muscle tone and pulse;
• a visual examination of the arms, the neck and, if exposed, the legs for evidence of injection sites.

Read that list as a client rather than as a lawyer. A large part of it is the officer looking at you and writing down what they think they see. Pupil size, muscle tone, and the quality of a balance test are observations, not measurements, and the conclusions drawn from them depend on training and on comparison against expected ranges.

What the evaluation produces is a category, not a substance and not a dose. Under section 320.28(4) and (5), where the evaluating officer concludes that the person's ability to operate was impaired by a type of drug on the statutory list, the officer shall identify the type or types. There are seven of them.

The right hand column describes how these medication classes are commonly classified in pharmacology. It is not a statutory classification, and nothing in the Criminal Code says that a particular pill belongs in a particular box. That gap is worth knowing about, because the identification of a category is a step in the Crown case, not a self proving fact.

What the evaluation cannot do is measure anything about your blood. It produces an opinion about a class of drug and about impairment. The concentration question belongs to a laboratory, and that is the subject of the next section.

"The blood test found my medication in it." What section 320.31 says that result actually proves

Less than most people assume, and the wording of section 320.31 is unusually precise about it.

Start with who can take the sample. Under section 320.28(6), blood may be taken only by a qualified medical practitioner or a qualified technician, and only if that person is satisfied that taking the sample would not endanger the person's health. Those are conditions on the taking, and they are provable facts rather than formalities.

Now the analysis. Section 320.31(2) makes an analyst's certificate proof of the blood drug concentration at the time when the sample was taken, in the absence of evidence tending to show that the analysis was performed improperly. Read those italicised words again. The statute proves a number as at the moment of the needle. It does not prove a number as at the moment you were driving, and those two moments are often separated by a long stretch of the night.

Section 320.31(3) then closes a door. Evidence about how much you consumed, about absorption or elimination rates, or a calculation built on those things, does not count as evidence that the analysis was performed improperly. So the pharmacology argument cannot be smuggled in through the back of subsection (2). It has to be made on its own terms.

Then comes the presumption in section 320.31(6), which is the provision most commonly misdescribed. Where the sample contains a drug of the type the evaluating officer identified, that drug is presumed, in the absence of evidence to the contrary, to be the drug present in the person's body at the time of operation and, on proof of the person's impairment, to have been the cause of that impairment.

The officer's opinion is treated the same way. Section 320.31(5) makes an evaluating officer's opinion about impairment by an identified type of drug admissible without qualifying the officer as an expert, and in R v Bingley, 2017 SCC 12, the Supreme Court confirmed that no voir dire under the ordinary expert evidence rules is required, because Parliament had already established the qualification. Bingley was decided on the wording of the former section 254(3.1), and the successor provisions are now sections 320.28(2) and 320.31(5), so the numbering has moved even though the scheme has not.

But the second half of Bingley is the half that matters at trial. The weight of that opinion is always for the trier of fact, and the opinion is not conclusive of impairment. It goes in. It does not decide the case.

"There is no legal limit for my medication." Why paragraph (1)(a) does not need a number

This one is usually correct on the facts and wrong about the consequence.

The Criminal Code creates two quite different drug driving offences. Section 320.14(1)(c) is the per se offence. It is committed by having, within two hours after ceasing to operate, a blood drug concentration equal to or exceeding the concentration prescribed by regulation for that drug. It needs a number, and it does not require anyone to prove that you drove badly. Section 320.14(1)(a) is the impairment offence. It needs proof of actual impairment, and it does not involve a number at all.

The regulations prescribe concentrations for a short list of substances. For the overwhelming majority of prescription medications, no concentration has been prescribed at all, which means paragraph (1)(c) simply has nothing to bite on. The Crown cannot prosecute a per se offence where Parliament has never set the limit.

So a prescription medication case is almost always a paragraph (1)(a) case. And that is a much harder prosecution to run. Instead of producing a certificate with a figure on it, the Crown has to assemble a picture: the driving that drew attention in the first place, what the officer observed and recorded, the coordination tests, the evaluation, and the toxicology, and then persuade a court that the picture proves impairment of the ability to drive beyond a reasonable doubt.

Every one of those components is contestable in a way a number is not. The absence of a legal limit is not a gap in the law that protects you. It is a shift in what the Crown has to prove, and it moves the fight onto ground where the defence has far more to work with. Where the medication does have a prescribed concentration, the analysis changes completely, and we set out the substances and the figures on our drug related DUI page.

"I said no to the blood sample because I did not understand." Refusal as a separate offence

Refusal is not a way of avoiding the charge. It is a second charge, and on a first offence it carries a heavier minimum than the impaired driving allegation it was meant to avoid.

Section 320.15(1) provides that everyone commits an offence who, knowing that a demand has been made, fails or refuses to comply, without reasonable excuse, with a demand made under section 320.27 or section 320.28. It covers the roadside demands and the station demands alike, so refusing the coordination tests, the screening sample, the evaluation or the blood all fall inside it.

The penalty is set by section 320.19, and section 320.19(4) fixes a minimum fine of $2,000 for a first offence of refusal. The minimum for a first impaired driving conviction is $1,000. So the refusal doubles the statutory floor.

Three elements are worth separating out, because each is a place where a case can be won.

• Knowledge of the demand. The section requires that the person knew a demand had been made. A muttered instruction in a noisy roadside environment, or a demand delivered to a person who does not speak English well, raises a real question about whether that element is proved.
• Failure or refusal. Not every failure to produce a sample is a refusal. A person who tries and cannot, for a physical or medical reason, has not necessarily refused anything.
• Reasonable excuse. The statute expressly builds this in. What counts as a reasonable excuse is assessed on the evidence in the particular case, and a genuine medical inability is very different from a decision to say no on principle.

What almost never works is the explanation clients give first: that they said no because they were confused, or frightened, or thought they were entitled to wait. Those are understandable human reactions and they are not, without more, an answer to the charge. If you are reading this before anything has happened, that is the single most useful sentence on this page.

"My doctor and my pharmacist never told me not to drive." Where the medical explanation helps

It helps in some places and it does nothing at all in others, and the difference is worth understanding before you spend money building the wrong record.

Where it does not help is the bare question of liability under paragraph (1)(a). The offence asks whether your ability to operate was impaired by a drug. It does not ask whether you were warned, whether you read the insert, or whether you expected the effect. A person who took the medication exactly as directed and was genuinely surprised by what it did has still, on the face of the section, driven while impaired by a drug.

The Supreme Court has looked at the edge of that problem. In The Queen v King, [1962] SCR 746, the Court considered whether a driver who becomes impaired by a drug administered to him, without knowing that it would impair him, can be said to have voluntarily driven in that state. The case is old and it arose on very particular facts, and it is best treated as an illustration of a live question rather than as a shortcut for anyone who says nobody warned them.

Where the medical picture genuinely earns its keep is in three other places.

• Causation. A stable, long standing therapeutic dose that the client has driven on safely for years undercuts the inference that this medication caused these observations on this night. Prescribing records, dose histories and pharmacy dispensing dates all speak to that.
• Alternative explanation. A treating physician can sometimes explain the very signs the evaluation recorded. A neurological condition, a recent injury, an eye condition, or a sleep disorder can each account for observations the officer attributed to a drug.
• Sentence. Where a conviction is the realistic outcome, the difference between misuse and a person following medical direction is a real part of what a court hears.

What all three have in common is that they need documents. Get the pharmacy printout, the prescribing history, and any note about a recent dose change into your lawyer's hands early, because the value of that material drops sharply once positions have hardened.

"It is my first offence, so I will get a discharge." What section 320.19 actually requires

Section 320.19 sets out what the court must impose, and the minimums apply whichever way the Crown elects to proceed. That last point surprises people, because on most hybrid offences a summary election softens the exposure. Here it does not touch the floor.

Two refinements matter on a drug file. The escalating minimum fines in section 320.19(3), the ones tied to how high a reading was, apply only to section 320.14(1)(b), which is the blood alcohol paragraph. They do not attach to a drug impaired charge. And the $2,000 minimum in section 320.19(4) applies to a first refusal, not to the impaired driving offence itself.

So the honest answer to the client belief in this heading is that section 320.19 requires the court to impose at least the minimum fine on a first conviction. Planning a case on the assumption that a first offence produces no penalty at all is planning on the wrong footing. What can be argued about is whether there should be a conviction in the first place, which is where the effort belongs.

"I need my licence for work." The prohibition and the provincial suspension running alongside it

Two separate authorities take your licence away for two separate reasons, and they do not wait for each other.

The court order. Section 320.24(1) and (2) require the sentencing court to make a driving prohibition order on a finding of guilt under section 320.14(1). The period is not less than one year and not more than three years on a first offence, not less than two years and not more than ten on a second, and not less than three years on each subsequent offence, and each of those periods runs on top of any term of imprisonment imposed. Section 320.24(10) then fixes the absolute period before an ignition interlock can be considered: on a first offence, whatever period the court fixes, which may be none; three months on a second offence; six months on a subsequent one.

Ontario. The province acts under its own authority and it acts first. According to the Ministry of Transportation, a driver who performs poorly on a drug recognition evaluation, or who fails or refuses a demand, receives an immediate roadside 90 day licence suspension under section 48.3.1 or section 48.3 of the Highway Traffic Act, a seven day vehicle impoundment under section 48.4, an eight hour education course and a $550 penalty on a first occasion, plus a reinstatement fee. None of that requires a conviction, or even a trial date.

On conviction the provincial ladder is steeper again, and section 41 of the Highway Traffic Act is what drives it: at least a one year suspension on a first conviction with mandatory education or treatment and an ignition interlock condition for at least a year; at least three years on a second conviction within ten years, with interlock for at least three years and a mandatory medical evaluation; a lifetime suspension on a third conviction within ten years, reducible after ten years if criteria are met, with interlock for at least six years; and a lifetime suspension with no possibility of reduction on a fourth. Drivers who are 21 or under, who hold a G1, G2, M1 or M2 licence, or who drive commercially face a zero tolerance rule: no drugs and no alcohol in the system at all.

The practical consequence is that the licence question has to be handled on two tracks from the first week. Anyone whose employment depends on driving should be told plainly that the ninety days at the roadside are not a sentence, cannot be appealed as though they were, and will run their course while the criminal charge is still at an early stage.

Why clients bring medication cases to Kazandji Law

A prescription medication charge is a paragraph (1)(a) case almost every time, which means the Crown has no number to fall back on and the whole file turns on observations, procedure and the qualifications behind an opinion. That is technical work, and it rewards a defence that reads the disclosure closely rather than one that treats every impaired file the same way.

Kazandji Law is led by founding partner Fadi Matthew Kazandji and serves clients across the Greater Toronto Area from four locations:

• Toronto (head office): 180 John Street, Unit 320, Toronto, Ontario M5T 1X5, close to the Ontario Court of Justice at 10 Armoury Street.
• Thornhill: 7191 Yonge Street, Suite 310, serving Markham, Richmond Hill and Vaughan, with York Region matters heard in Newmarket at 50 Eagle Street West.
• North York: convenient for clients north of the 401.
• Oakville: serving Halton Region.

We act on the full range of driving offences, from impaired driving and medical marijuana DUI charges to dangerous driving, and across criminal defence generally. If you were held for a hearing, our page on bail and bail hearings explains what happens next, and what to expect after being charged covers the wider process. Clients in York Region can start at our Markham criminal defence page, and past results are on our case results page.

Prescription medication and impaired driving: the questions we hear most

This page sets out general legal information about section 320.14 of the Criminal Code and the provisions and regulations that surround it, current as of July 2026. Provincial consequences are described from published Ministry of Transportation material. This is not legal advice, and reading it does not create a lawyer and client relationship. Every file turns on its own facts and its own disclosure. If you have been charged after taking prescribed medication, speak to a criminal defence lawyer about your own circumstances.