R. v. Hughes
70 C.C.C. (2d) 42
The accused was stopped and failed an A.L.E.R.T. test. The accused was then taken to the local RCMP detachment where he failed an approved screening test. Three tests had to be administered as the second test reading had a difference greater then 20 points of the first test. At trial, the accused introduced expert evidence of a former RCMP officer who had possession of an approved screening device and performed a simulation test to determine that the accused would have been below the legal limit. The trial judge instructed the jury to disregard the simulation and to disregard the erroneous second reading.
The trial judge erred in telling the jury to disregard the evidence. The trial judge should have told the jury that if the evidence raised a reasonable doubt, then the accused should be acquitted on the charge of over 80.