If a person refuses or fails to comply with the breath demand by, for example saying "no" or faking blowing etc., they will then be charged with refusing or failing to comply with a breath demand or providing a breath sample. The Crown will be required to prove beyond a reasonable doubt that the refusal to provide a breath sample or failure to comply was ‘final and unequivocal’.
If the Crown is able to prove a ‘final and unequivocal’ refusal, there are still defences to refusing to provide a breath sample such as having a ‘reasonable excuse’ not to provide a sample.
Many of the same ‘reasonable excuse’ defences apply to both refusing a roadside screening device and refusing an intoxilyzer breath demand. (See What Happens When a Person Refuses To Provide a Roadside Sample)
The courts have found many different reasons to be reasonable excuses. One example is having a health problem preventing the person from providing a proper sample. Another example of a reasonable excuse is demonstrating that the person was being mistreated by the police throughout the breath testing procedure and this "animosity" was playing on their mind at the time they refused. The many reasonable excuse defences are too numerous to list and the list is not closed. Each individual refusal factual situation, must be examined to see if there is a valid defence. As a general rule, a person who is under arrest should always comply with a demand to provide breath samples. Although there are occasionally exceptions to the general rule, the advice that an experienced DUI lawyer will always provide to a detainee/person under arrest is that they should always provide a breath sample upon demand. It is too risky, for example, to refuse to provide a breath sample and hope your case turns out “after the fact” to be one of the narrow exceptions.