James G. Wigmore, Forensic Toxicologist, Speaker, Author

An American criminal lawyer recently enquired about a female asthmatic client he had who was deemed by an arresting officer to have refused to provide a proper breath sample into a “breathalyzer”.  The legal consequences of such an act are significant and even more serious in Canada. In Canada, if someone does not provide a suitable breath sample into the roadside screening device and/or two suitable breath samples into the evidential breath testing instrument, they can face a criminal charge, and if convicted, obtain the same penalties as if they had blew over 0.08 g/100mL.  Since this issue is so serious, I have included a separate section on “Ability to Provide Breath Sample” in Wigmore on Alcohol consisting of twelve studies.

In order to provide a proper breath sample into a breath testing instrument, a forced vital capacity (FVC) of approximately 2.5 litres is required (WOA30301-3).  FVC is the volume of breath that can be exhaled after a maximum inhalation and is an indication of lung size and health.  In addition to the deliberate and conscious refusal of breath testing, criminal lawyers should be aware that the following factors could cause a person not to deliver a proper breath sample:

  • Height, Age and Gender: Lung size or FVC varies according to the height, age and gender of the subject.  A young tall man (age 20 years, height 6’2”) has a predicted FVC of approximately 6.2 litres and should, generally, have no problem providing a breath sample into a breath testing instrument.  Whereas a 60 year old woman 5’0” in height, has a predicted FVC of approximately 2.5 litres and, thus, could have difficulty providing a suitable breath sample.

  • Lung Disease:  Various lung diseases can significantly lower the FVC of a subject (WOA30304-8) making it difficult to blow into a breath testing instrument and provide a legitimate defense for the criminal lawyer.  For a more detailed discussion of the effect of lung disease on breath alcohol testing, click on this paper on lung disease.

  • Poor instructions: Poor instructions by the police may contribute to a person being unable to provide a breath sample (WOA30305). Police Officers should encourage the subject to “blo longer and keep blowing, keep blowing, keep blowing” as opposed to directing the subject to “blow harder”. For most individuals, blowing harder often results in the lungs being emptied too soon. I have been involved in cases where the police officer actually conducted a breaath test themselves in order to demonstrate to the subject how to blow properly. (Yes all the police breath test results were zero!)

  • Defective Mouthpiece:  If the mouthpiece has a hole in it or a piece of plastic is stuck in it from the manufacturing process or during the removal of the mouthpiece from the plastic bag, airflow may be blocked.  A criminal lawyer will want to ensure that the mouthpiece is examined closely in cases of a refusal.

  • Lip Sealing:  A proper breath sample may not be provided if a person has trouble forming a proper lip seal as a result of local dental anesthesia (WOA30310) or a medical condition which reduces feeling in the lips.

  • Slipping Upper Dentures:  Upper dentures which are slipping can decrease the ability to provide a proper breath sample and another legitimate reason for a breath sample refusal.  To learn more about the effect of upper dentures on breath sampling, please click on this paper on Slipping Dentures.

Not all refusals are the result of the deliberate and conscious refusal of breath testing and anyone involved in a refusal case should contact a DUI, DWI or criminal lawyer for consultation.