DUI Metrology Dictionary

Contradiction of the instrument's result (defence)

Pre Bill C-2, the defence could rebut the presumption of identity by leading a defence of the client's evidence of alcohol consumption together with evidence of a toxicologist declared an expert on absorption, elimination, and distribution of ethyl alcohol in the human body. The expert would then do a calculation of blood alcohol concentration at time of driving or care or control which could raise a reasonable doubt, pre C-2, as to the Intoxilyzer results. No evidence would be led as to the reasons for the unreliability of the Intoxilyzer on the particular occasion. Many Judges disliked the defence raising issues about the Intoxilyzer reliability because all they were concerned about was reasonable doubt based on drinking scenario and toxicological evidence. Critics labelled this as the "two beer" defence and convinced Parliament to eliminate this defence of truth.