What Bill C-46 Changed
Bill C-46 was the most significant reform of Canada’s impaired driving laws in decades. It replaced the old Criminal Code provisions (sections 253 through 259) with an entirely new framework under Part VIII.1, spanning sections 320.11 through 320.4. The new provisions came into force on December 18, 2018.
The changes were not cosmetic. Bill C-46 introduced fundamentally new police powers, new offences, higher penalties, and new evidentiary rules that affect how every impaired driving case in Canada is investigated, prosecuted, and defended.
Mandatory Alcohol Screening
The single most significant change was the introduction of mandatory alcohol screening under section 320.27(1). Before Bill C-46, a police officer needed reasonable suspicion that a driver had alcohol in their body before they could demand a roadside breath sample. Under the new law, any officer with an approved screening device (ASD) can demand a breath sample from any lawfully stopped driver — no suspicion required.
This means that at a routine traffic stop for a broken tail light, an expired sticker, or even a RIDE checkpoint, an officer can immediately demand you blow into an ASD. You are required to comply. Refusing is a criminal offence under section 320.15, carrying the same penalties as impaired driving.
The practical impact has been significant. More drivers are being screened, more ASD “fail” results are being generated, and more charges are being laid. For defence lawyers, mandatory screening has shifted the focus from whether the officer had grounds for the ASD demand to whether the initial stop itself was lawful. If the stop violated section 9 of the Charter (arbitrary detention), the entire chain of evidence that follows — the ASD result, the arrest, the station breath test — may be excluded.
The Two-Hour Rule
Bill C-46 introduced a new offence structure under section 320.14(1)(b): it is now an offence to have a blood alcohol concentration at or above 80 mg per 100 mL of blood within two hours of ceasing to operate a conveyance. Under the old law, the Crown had to prove your BAC at the time of driving. Under the new law, the Crown only needs to prove your BAC within the two-hour window.
This was designed to eliminate the “bolus drinking” defence — where an accused would claim they had consumed alcohol immediately before driving and it had not yet been absorbed into their bloodstream at the time of driving. It also means police can charge you even if they find you at your home after you have arrived, provided the breath test occurs within the two-hour window.
The two-hour rule includes a statutory exception: you cannot be convicted if you consumed alcohol after driving and had no reasonable expectation of being required to provide a breath sample. This “intervening drink” defence requires the accused to demonstrate that the post-driving consumption accounts for the BAC reading, and that they had no reason to expect police contact.
New Section Numbers
The reorganization of the Criminal Code means that anyone researching impaired driving law must use the current section numbers. The old numbers are no longer in force for offences committed after December 18, 2018.
| Offence | Old Section | New Section |
|---|---|---|
| Definitions | s. 253 | s. 320.11 |
| Dangerous operation | s. 249 | s. 320.13 |
| Impaired / over 80 | s. 253 | s. 320.14 |
| Refusal | s. 254(5) | s. 320.15 |
| Failure to stop after accident | s. 252 | s. 320.16 |
| Penalties | s. 255 | s. 320.19–.21 |
| ASD demand / breath demand | s. 254 | s. 320.27–.28 |
Higher Maximum Penalties
Bill C-46 increased the maximum penalties for impaired driving offences:
- Standard offence (indictment): maximum increased from 5 years to 10 years imprisonment
- Causing bodily harm: maximum increased from 10 years to 14 years imprisonment
- Causing death: maximum increased from 14 years to life imprisonment
The mandatory minimum penalties remained largely the same: a $1,000 fine and one-year driving prohibition for a first offence, 30 days imprisonment and a two-year prohibition for a second, and 120 days imprisonment and a three-year prohibition for a third or subsequent offence.
Drug-Impaired Driving Provisions
Bill C-46 was enacted alongside the legalization of cannabis (Bill C-45), and it introduced new provisions specifically targeting drug-impaired driving. The new law created per se drug offences with prohibited blood drug concentrations:
- THC (cannabis): 2 to less than 5 ng/mL of blood is a summary offence (maximum $1,000 fine); 5 ng/mL or more triggers the same penalties as impaired driving
- THC + alcohol: having THC at or above 2.5 ng/mL combined with a BAC at or above 50 mg per 100 mL is an offence with the same penalties as impaired driving
The law also formalized the use of Drug Recognition Evaluators (DREs) and authorized police to demand oral fluid samples at the roadside using approved drug screening equipment. However, the practical deployment of oral fluid screening devices has been limited, and most drug-impaired driving cases continue to rely on DRE evaluations and blood testing.
New Evidentiary Rules
Bill C-46 changed the evidentiary rules for breathalyzer results. Under section 320.31(1), the results of the approved instrument are now conclusive proof of the accused’s BAC, unless the accused can demonstrate that the instrument was malfunctioning or operated improperly. This reversed the previous framework, which allowed the accused to raise a reasonable doubt about the accuracy of the results through evidence of their drinking pattern (“evidence to the contrary”).
This change was intended to reduce the effectiveness of the “Carter defence” (named after R v. Carter), where toxicologists would testify that the accused’s drinking pattern was inconsistent with the breathalyzer reading. Under Bill C-46, this type of evidence is no longer sufficient on its own — the accused must point to a malfunction or operational error in the instrument itself.
For defence lawyers, this shifted breathalyzer challenges toward technical grounds: maintenance records, calibration logs, technician qualifications, and the condition of the instrument at the time of testing.
How the New Laws Affect Your Defence
Bill C-46 changed the landscape, but it did not eliminate defences. It created new ones. Mandatory alcohol screening makes the legality of the initial stop more important than ever — if the stop was unlawful, everything that follows falls. The two-hour rule opened new issues around post-driving consumption. The new evidentiary rules shifted breathalyzer challenges toward technical grounds where maintenance and calibration records can be decisive.
Impaired driving law is now more technical and more procedurally complex than it was before 2018. That complexity creates opportunities for experienced defence counsel to identify errors and challenge the Crown’s case at every stage.
If you have been charged with impaired driving under the new framework, the details of your stop, arrest, and breath testing process all need to be examined by someone who understands how Bill C-46 works in practice. Contact RH Criminal Defence to discuss your case.