The right defence always depends on the facts, and no approach works in every case. What follows is general information, not legal advice about your situation.
How does roadside testing work in Ontario?
Most impaired driving investigations begin at the roadside. Police may stop a driver at a RIDE checkpoint, for a traffic violation or after a collision. Once you are lawfully stopped, an officer with an approved screening device can demand a breath sample, even without any suspicion that you have been drinking. This is known as mandatory alcohol screening.
A roadside result is mainly a screening tool. It helps the officer decide whether there are grounds for a formal breath test. A fail on the screening device usually leads to an arrest and a demand for breath samples into an approved instrument at the station.
Police can also investigate drug impairment at the roadside, including by demanding an oral fluid sample, and may demand a drug recognition evaluation at the station. Drug-impaired driving charges often turn on how officers carried out those steps.
A defence review of the roadside stage asks questions such as:
- Was the stop itself lawful, and had police lawfully stopped the driver before the officer made the demand?
- Did the officer have an approved screening device when they made the demand?
- Did the officer make the demand promptly and in proper form?
- In a refusal case, did the driver truly refuse, or did they try and fail to provide a suitable sample?
That last question is central to many breath test refusal cases. If you want to know what to expect at a check stop, see our article on how RIDE checkpoints work. In one of our Toronto files the roadside demand itself failed; read how an unlawful roadside demand led to a dismissal.
How can breathalyzer evidence be challenged?
In an over 80 prosecution, the Crown relies on breath samples taken at the station with an approved instrument. In Ontario, that instrument is the Intoxilyzer 8000C. The readings can look conclusive, but they are only as reliable as the machine, the operator and the process behind them.
Disclosure is where a breath defence begins. It should include the instrument's records and maintenance logs, the breath technician's notes and the station video. We review that material for issues such as:
- Maintenance and calibration. Gaps or irregularities in the instrument's service and test records.
- Operator procedure. Whether the qualified technician followed the required steps and recorded them accurately.
- Timing. When the technician took the samples compared with when driving ended, since the offence concerns your blood alcohol concentration within two hours of operating.
- Observation period. Whether the technician watched you before testing to rule out mouth alcohol from burping or regurgitation.
- Medical and physical factors. Conditions such as acid reflux that may affect a result.
Readings close to a threshold deserve extra attention. A blood alcohol concentration of 120 mg or more is an aggravating factor at sentencing, and higher readings raise the minimum fine for a first offence. Our article on the breathalyzer detection window explains more about how alcohol moves through the body, and an over 80 dismissal over instrument records from our files shows why maintenance logs matter.
What Charter rights apply during a DUI investigation?
The Canadian Charter of Rights and Freedoms limits what police can do during an impaired driving investigation. The rights that come up most often are:
- Section 8: protection against unreasonable search or seizure. Taking breath or blood samples is a seizure, so the demand must be lawful.
- Section 9: protection against arbitrary detention. A detention must have a lawful basis.
- Section 10(b): the right to retain and instruct counsel without delay, and to be told about that right. After an arrest, police must give you a reasonable opportunity to contact a lawyer, and delays or refusals can become a Charter issue.
When police breach a right, the defence can apply to exclude the evidence under section 24(2). The court decides whether admitting the evidence would bring the administration of justice into disrepute, using the framework set by the Supreme Court of Canada in R. v. Grant. If the court excludes key evidence such as the breath results, the Crown may not be able to prove the charge. That is what happened when charges stayed after counsel denial in one of our matters.
Delay can also matter. You have the right to be tried within a reasonable time, and in R. v. Jordan the Supreme Court set a presumptive ceiling of 18 months for cases in the Ontario Court of Justice. Unreasonable delay beyond that ceiling can lead to a stay of the charges.
What happens after a DUI arrest?
After the breath tests, police release most drivers with paperwork setting a first court date. Several things then happen at once, on separate tracks.
Provincial consequences start immediately. If you blew over 80, refused or an evaluator found you impaired by a drug, Ontario imposes a 90-day Administrative Driver's Licence Suspension, a 7-day vehicle impoundment and an administrative monetary penalty. These apply even though you have not been convicted. Our article on the 90-day ADLS suspension explains how it works.
The criminal case begins. At your first appearance in the Ontario Court of Justice, the Crown provides initial disclosure. Your lawyer reviews it, requests anything missing, such as video or instrument records, and assesses the strength of the case.
Some decisions are time-sensitive. Ontario's reduced suspension program, for example, can let eligible first offenders who resolve their case early drive sooner with an ignition interlock, but the eligibility rules and deadlines are strict. Getting advice early keeps your options open, whether you plan to contest the charge or resolve it.
The case resolves. The Crown may withdraw a charge, the parties may negotiate an outcome, or a judge may decide it at trial. You make the final decision after hearing a clear recommendation. If there is a conviction, the penalties described in our penalties guide apply.
For a checklist of first steps, read what to do if you are charged with a DUI, or find your offence on our overview of DUI charges. To see how these defences have played out in practice, review the examples on our case results page, and if you are still deciding whether to contest the charge, read is it worth fighting a DUI in Ontario.