If the driver is found with more than the legal limit of 35 microgrammes of alcohol per 100 millitres of breath, or more than 80 milligrammes of alcohol per 100 millitres of blood, he/she is deemed to have broken the law and it does not matter whether the driver has perfect control of the vehicle, when caught.
Even when the alcohol level is under the legal limit, the driver can still be convicted if it is shown that he/she did not have proper control of the vehicle as a result of alcoholic intoxication.
Safe Drive Breathalyzer