How can the Crown prove impaired driving beyond a reasonable doubt at trial when the investigating officer only had a reasonable suspicion of impairment at the roadside? By presenting further evidence gathered by the officer. For example: further signs of impairment noted after the arrest, a warned statement from the accused about alcohol consumption, written witness statements from civilians who called police about the driving they had witnessed. In the case of Mr. Wilson, the Saskatchewan Court of Appeal upheld the trial judge's conviction for impaired driving even though at the outset of the investigation the officer only had a reasonable suspicion of impairment and therefore used an approved screening device:
[C]onviction on the impaired driving charge pivots not on the judgment of the arresting officer but rather on the weight of the whole body of evidence before the trial judge, which cogently supports the conclusion that he operated a motor vehicle while his ability to do so was impaired by alcohol. R. v. Wilson, 2013 SKCA 128