The Legal Limit: 80 mg per 100 mL
Under section 320.14(1)(b) of the Criminal Code, it is a criminal offence to have a blood alcohol concentration (BAC) at or above 80 milligrams of alcohol per 100 millilitres of blood within two hours of operating a conveyance. This is commonly referred to as the “over 80” charge.
The offence is a per se offence — it does not require the Crown to prove that your ability to drive was impaired. If your BAC was at or above 80 mg, the offence is made out, regardless of whether you appeared perfectly sober. This is different from the impaired driving charge under section 320.14(1)(a), which requires proof of actual impairment.
Ontario’s Three Tiers
Ontario operates a three-tier system for blood alcohol levels, each with different legal consequences:
| BAC Range | Category | Consequences |
|---|---|---|
| 0 – 49 mg | Below limit | None (for fully licensed drivers) |
| 50 – 79 mg | Warn range (HTA) | Roadside suspension, no criminal charge |
| 80 mg + | Over 80 (Criminal Code) | Criminal charge, criminal record if convicted |
The warn range (50 to 79 mg) is an Ontario administrative penalty, not a criminal offence. A first warn range result triggers a 3-day roadside licence suspension. A second triggers a 7-day suspension and a mandatory education program. A third triggers a 30-day suspension, mandatory treatment, and an ignition interlock device for 6 months. These are imposed by the officer at the roadside and do not result in a criminal record.
Novice drivers (G1, G2, M1, M2 licence holders) and drivers under 21 must have a BAC of zero. Any detectable alcohol is a violation.
How the Breathalyzer Works
When you are arrested for impaired driving and taken to the station, you are required to provide two breath samples on an approved instrument. In Ontario, the instruments most commonly used are the Intoxilyzer 8000C and the Datamaster DMT. These devices measure the alcohol concentration in your breath and convert it to a blood alcohol equivalent using a partition ratio.
The two samples are taken approximately 15 to 20 minutes apart. The qualified technician must observe you for a mandatory period before the first sample to ensure that you have not consumed anything, vomited, or burped — events that could introduce mouth alcohol and produce a falsely elevated reading.
Both readings must agree within an acceptable range. If they diverge significantly, it may indicate an instrument malfunction or an interfering substance. The lower of the two readings is used.
Where Over 80 Charges Fall Apart
A breathalyzer reading above 80 mg is not the end of the analysis. It is the beginning. The Crown must prove that the reading is accurate, admissible, and was obtained through lawful means. There are multiple points where the Crown’s case can fail.
Instrument Maintenance and Calibration
Approved instruments must be regularly maintained and calibrated according to the manufacturer’s specifications and the standards set by the Alcohol Test Committee. The defence is entitled to disclosure of the instrument’s maintenance logs, calibration records, and repair history. If the instrument was overdue for maintenance, had a history of malfunctions, or was not calibrated within the required timeframe, the reliability of the reading can be challenged.
Technician Errors
The breath test must be administered by a qualified technician — an officer who has received specific training and certification on the approved instrument. The technician must follow a precise protocol: confirm the observation period, verify the instrument’s ready state, obtain two samples within the required time window, and document the results. Deviations from this protocol can form the basis of a challenge.
Mouth Alcohol and Gastric Reflux
The breathalyzer measures alcohol in deep lung air. If alcohol is present in the mouth — from a recent drink, from burping or vomiting, from gastric reflux, or even from certain dental conditions — the reading will be falsely elevated. The mandatory observation period is designed to prevent this, but if the observation period was not properly conducted, the defence can argue that mouth alcohol contaminated the sample.
The Two-Hour Rule
Under the current law (post-Bill C-46), the Crown must prove your BAC was at or above 80 mg within two hours of driving. If the breath test was conducted more than two hours after you last operated the vehicle, the Crown’s case faces an additional hurdle. The defence can also raise evidence of post-driving consumption — if you consumed alcohol after parking the vehicle and before the breath test, that alcohol may account for the elevated reading.
Charter Violations
The entire chain of evidence — from the traffic stop through the breath test — must comply with the Charter. Common Charter grounds for excluding breathalyzer evidence include:
- Section 9 (arbitrary detention): the initial stop was unlawful
- Section 10(b) (right to counsel): the accused was not informed of the right to a lawyer, or was not given a reasonable opportunity to contact one before the breath test
- Section 8 (unreasonable search): the breath demand was made without lawful authority
If any of these rights were violated, the breathalyzer results may be excluded under section 24(2) of the Charter. Without the breathalyzer results, the Crown’s over 80 case collapses.
What to Do If You Are Charged
If you have been charged with over 80, the most important step is to have the disclosure reviewed by a criminal defence lawyer before making any decisions about your case. The disclosure package will include the breathalyzer certificates, the technician’s notes, the officer’s notes, and any video evidence. The instrument’s maintenance and calibration records can be requested as additional disclosure.
Do not assume that a reading above 80 mg means you will be convicted. Over 80 charges are regularly challenged on technical, procedural, and constitutional grounds. RH Criminal Defence has experience challenging breathalyzer evidence and defending over 80 charges at courthouses across Ontario, including Brampton, Mississauga, Newmarket, and Old City Hall. Contact the office to discuss your case.