Breath-test results can play a significant role in an impaired-driving prosecution. A careful review may consider the circumstances of the demand, the timing of samples, the testing process, instrument records, maintenance and calibration information, operator procedures and disclosure.

The significance of a breath result depends on the specific charge and the surrounding evidence. A lawyer can assess whether the prosecution has established the required elements of the offence and whether any evidentiary or constitutional issues arise.

Impaired-driving allegations are not limited to alcohol. The Criminal Code also addresses operation while impaired by a drug or by a combination of alcohol and drugs.

Drug-impaired driving cases can involve different forms of evidence and investigation. The defence may need to examine police observations, screening or testing procedures, expert evidence and the circumstances in which samples were obtained.

Police procedure can be an important part of an impaired-driving defence. Depending on the circumstances, counsel may review the legality of the detention, the timing and nature of demands, access to counsel, the collection of evidence and other steps taken during the investigation.

The Canadian Charter of Rights and Freedoms protects important rights of people who are detained or arrested. Whether a Charter issue exists depends on the facts and requires a careful review of the evidence.