15 min read · March 2025
Impaired driving is the most frequently prosecuted criminal offence in Ontario courts. The 2018 amendments to the Criminal Code (Bill C-46) substantially changed the legal framework — expanding police powers with mandatory alcohol screening, adding drug-impaired driving offences, and narrowing the range of defences available. This guide covers the offences, the evidence, the Charter arguments, and the sentencing consequences.
Impaired driving offences are found in Criminal Code Part VIII.1, ss. 320.11–320.4, as amended by Bill C-46 in force December 2018. The primary offences:
| Section | Offence | Key Element |
|---|---|---|
| s. 320.14(1)(a) | Impaired operation | Operation of a conveyance while ability to operate is impaired by alcohol or drug — no BAC threshold required |
| s. 320.14(1)(b) | Over 80 | Operation with BAC 80mg/100mL or over — concentration-based offence, no impairment proof needed |
| s. 320.14(1)(c)/(d) | Drug-impaired — blood drug concentration (BDC) | Operation with blood drug concentration equal to or exceeding prescribed limits (cannabis, cocaine, methamphetamine, GHB, etc.) |
| s. 320.14(2) | Aggravated impaired operation (BAC 120+) | BAC equal to or exceeding 120mg/100mL — aggravated form with higher mandatory minimums |
| s. 320.14(3) | Aggravated impaired operation (BAC 160+) | BAC equal to or exceeding 160mg/100mL — highest mandatory minimums |
| s. 320.15 | Refusal to comply with demand | Refusal to provide breath/blood sample — same penalties as over 80 |
| s. 320.16 | Failure to stop after accident | Failure to stop at scene + reasonable belief impairment would be detected |
| s. 320.18 | Operation while prohibited | Operating while disqualified from driving |
Conveyance
The offence applies to any "conveyance" — defined in s. 320.11 to include motor vehicles, vessels, aircraft, and railway equipment. Operation of a boat while impaired is a Criminal Code offence, not just a provincial regulatory matter.
Section 320.27 of the Criminal Code, as amended by Bill C-46, introduced mandatory alcohol screening — the most significant change to impaired driving law in decades.
A peace officer who lawfully stops a driver may demand a breath sample into an ASD without any suspicion of alcohol consumption. Pre-Bill C-46, reasonable suspicion was required. The constitutional validity of mandatory screening was upheld by the Supreme Court in R v Sullivan; R v Brown 2022 SCC 19.
A peace officer who has reasonable grounds to suspect alcohol in the driver's body may also demand an ASD. This has broader application — it applies even when the officer did not stop the vehicle during a lawful check.
A Fail on the ASD provides reasonable grounds for a further demand for a breath sample on an approved instrument (Intoxilyzer). The ASD result itself is not evidence of the BAC at the time of driving — it only triggers the next step.
The evidentiary centerpiece of most impaired driving prosecutions is the certificate of a qualified technician showing the results of an approved instrument breath test (s. 320.31). The Code creates a presumption that:
Pre-Bill C-46: The accused could rebut the presumption by raising evidence of a malfunction or improper operation — the "Carter defence" (named after R v Carter).
Post-Bill C-46: The Carter defence was eliminated. Under s. 320.31(1), the only way to challenge instrument readings is to establish that there was an "approved instrument malfunction" or that the instrument was "operated improperly" — and even then, the accused must call evidence that if the instrument had been operating properly or had been operated properly, the result would have been below 80. The Supreme Court upheld the constitutionality of these changes in R v Sullivan.
Bill C-46 introduced blood drug concentration (BDC) offences alongside the existing alcohol offences. The prescribed blood drug concentration limits (O. Reg. SOR/2018-181):
| Drug | Limit (lower) | Limit (upper / aggravated) |
|---|---|---|
| THC (cannabis) | 2–5 ng/mL blood — summary conviction (lower limit) | 5 ng/mL or more — indictable or hybrid |
| Cocaine | 5 μg/L blood — lower limit offence | 50 μg/L — upper limit |
| Methamphetamine | 5 μg/L | 50 μg/L |
| MDMA (ecstasy) | 5 μg/L | 50 μg/L |
| GHB | 5 μg/L (above endogenous levels) | 50 μg/L |
| THC + alcohol combination | THC 2.5 ng/mL + BAC 50mg/100mL | Both thresholds simultaneously — indictable |
Drug-impaired driving investigations use Standard Field Sobriety Tests (SFST) and Drug Recognition Evaluations (DRE) conducted by specially trained officers. Blood samples are required for BDC analysis — the Intoxilyzer cannot detect drugs.
Post-Bill C-46, the Carter defence and evidence-to-the-contrary defence are eliminated. Available defences include:
| Defence | Basis |
|---|---|
| Approved instrument malfunction | s. 320.31: Establish the instrument was malfunctioning AND the proper reading would have been below 80 — both elements required |
| Improper operation of instrument | Establish the technician did not follow the approved method AND proper operation would have resulted in a sub-80 reading |
| Bolus drinking (last drink defence) | Evidence that accused consumed alcohol shortly before driving and BAC was under 80 at time of driving (not at time of testing 30+ min later) — very narrow post-Bill C-46 |
| Identity | Proof of identity of driver — relevant in some cases |
| Charter remedies | Evidence excluded under s. 24(2) if obtained in violation of ss. 8, 9, or 10(b) — see below |
| No reasonable grounds for demand | ASD demand under s. 320.27(2) required reasonable suspicion — if no suspicion existed, demand was unlawful → Charter s. 9 arbitrary detention |
| Accident reconstruction | For impaired operation charge (not over 80): challenge that the manner of driving was caused by factors other than impairment |
Charter arguments remain the most potent tool in impaired driving defence. Common arguments:
Upon arrest or detention, police must inform the accused of their right to retain and instruct counsel without delay and provide a reasonable opportunity to exercise that right. Common issues:
A breath demand is a search under s. 8. If the demand was made without lawful authority (no reasonable grounds for an approved instrument demand), the breath samples were taken in violation of s. 8.
A traffic stop is a detention. If the stop was pretextual (no highway traffic basis), the detention was arbitrary. Evidence obtained during an arbitrary detention may be excluded.
Charter-derived evidence (breath certificates, observations) is excluded under s. 24(2) if its admission would bring the administration of justice into disrepute. The three-part Grant test (R v Grant 2009 SCC 32) applies: seriousness of the Charter-infringing conduct; impact of the breach on the Charter-protected interests of the accused; society's interest in adjudication on the merits.
Impaired driving offences are hybrid (Crown election). Mandatory minimums apply regardless of election:
| Offence | 1st Offence | 2nd Offence | 3rd+ Offence |
|---|---|---|---|
| Over 80 / Impaired / Refusal (standard) | $1,000 fine + 1-yr prohibition | 30 days jail + 2-yr prohibition | 120 days jail + 3-yr prohibition |
| BAC 120–159mg/100mL (aggravated) | $1,500 fine + 1-yr prohibition | 60 days jail + 2-yr prohibition | 240 days jail + 3-yr prohibition |
| BAC 160+mg/100mL (aggravated) | $2,000 fine + 1-yr prohibition | 120 days jail + 2-yr prohibition | 1 year jail + 3-yr prohibition |
| Impaired causing bodily harm | Max 14 years (indictment) | Same | Same |
| Impaired causing death | Max life imprisonment | Same | Same |
Separate from the criminal process, Ontario's Highway Traffic Act imposes administrative penalties:
Ontario impaired driving matters proceed in the Ontario Court of Justice unless the Crown elects indictment or the accused elects Superior Court for indictable offences (causing bodily harm/death):
Diversion Program
Some Ontario courts offer diversion for first-time impaired driving charges — typically involving counselling, a fine, and a period of prohibition in exchange for a stay or withdrawal. Eligibility varies by jurisdiction and Crown practice. Not available in all cases and Crown discretion is broad.
Atticus helps Ontario criminal defence lawyers track court dates, disclosure deadlines, and Charter application timelines across all active files — with AI-powered morning briefings and document processing.
Start Free TrialOntario impaired driving charges include: s. 320.14(1)(a) impaired operation; s. 320.14(1)(b) over 80 (BAC 80mg/100mL+); s. 320.14(1)(c)/(d) blood drug concentration offences; s. 320.15 refusal to provide a sample; and aggravated forms for BAC 120+ and 160+. Bill C-46 (2018) significantly expanded the regime.
No. Refusal to provide an ASD breath sample is a Criminal Code offence under s. 320.15, carrying the same mandatory penalties as impaired driving. The Supreme Court upheld mandatory screening (no suspicion required) in R v Sullivan; R v Brown 2022 SCC 19.
First offence: $1,000 fine + 1-year driving prohibition. Second offence: 30 days imprisonment + 2-year prohibition. Third+ offence: 120 days imprisonment + 3-year prohibition. Aggravated forms (BAC 120+) carry higher mandatory minimums.
No. Bill C-46 eliminated the Carter defence (raising evidence that the instrument was malfunctioning or improperly operated to create reasonable doubt). Post-2018, an accused must establish an actual malfunction or improper operation AND prove the proper reading would have been below 80.