Même si le seuil de ce doute n'est pas très élevé — une odeur d'alcool suffit habituellement —, on a fait la preuve que la capacité des policiers à détecter les signes et symptômes de la consommation d'alcool varie considérablement.
However, police were not given the power to demand a breath test without a reasonable suspicion that the driver had consumed alcohol. Although the threshold for suspicion is not high—generally the smell of alcohol is sufficient—it has been demonstrated that police officers vary considerably in their ability to detect the signs and symptoms of alcohol use.
