The accused argued at trial that the margin of error on the Borkenstein Model 900A breathalyser was 10 mg. As a result, the accused argued that it was possible, based on his readings of 90 milligrams of alcohol in 100 milligrams of blood that the accused was within the legal limit.

Evidence to the contrary must be evidence to show that the blood alcohol level of the accused was within legal limits at the time of the offence. As no such evidence was provided at this trial, the is no evidence to the contrary in this case. Evidence to the contrary can not be evidence solely directed at defeating the scheme established by Parliament. Evidence is not evidence to the contrary when its only effect is to demonstrate in general terms the possible uncertainty of the elements of the scheme or the inherent fallibility of instruments which are approved under statutory authority.