Breathalyzer
"Breathalyzer" is a colloquial term — originally a brand name — for the evidentiary breath testing instrument used at police stations to measure a driver's blood alcohol concentration. The Criminal Code uses the term "Approved Instrument." Only listed instruments operated by qualified breath technicians can produce BAC readings admissible in court.
Mass Tsang's DUI lawyers examine every breathalyzer file for technical and Charter angles. For more, see our blog posts on the over 80 rule and how to fight an impaired driving charge.
How the testing works
After a fail on a roadside ASD or other grounds for an evidentiary demand, the driver is brought to the station. A qualified technician operates the Approved Instrument. Two breath samples are taken at least 15 minutes apart. The lower of the two readings is used as the BAC at the time of testing. Statutory presumptions in section 320.31 allow the court to read the BAC back to the time of driving, provided the sampling was done within statutory windows and the procedure complied with the rules.
Approved Instrument vs. Approved Screening Device
A common confusion is between the roadside ASD (a handheld screening device that produces PASS/WARN/FAIL) and the station-house Approved Instrument (which produces numerical BAC readings used in court). Only the latter prove the offence; the former only provide investigative grounds. Both must be listed by regulation and properly maintained.
Challenges to breathalyzer evidence
Common defence challenges to breathalyzer evidence include: timing of breath samples (the "as soon as practicable" requirement); whether two samples 15 minutes apart were actually taken; calibration and maintenance records of the instrument; qualifications of the breath technician; observance of waiting periods; mouth-alcohol scenarios (recent burping, regurgitation, or use of breath-spray); medical conditions affecting accuracy; and Charter-based challenges to the underlying stop or to the right-to-counsel implementation that preceded the testing.
Section 320.31 — narrowing the defences
Bill C-46 (2018) narrowed several pre-existing defences. The statutory presumption of BAC is now more difficult to displace — "evidence to the contrary" was largely removed and replaced with a narrow set of circumstances under section 320.31(1)(c), and most challenges now turn on Charter issues or technician/instrument problems.
Related glossary terms
