What are the tests used by the police and the courts to determine whether an accused was impaired by alcohol to the degree of impairing his ability to drive?

In R v. Landes 1997 CanLII 11314 (SK QB), [1997], S.J. No. 785, Justice Klebuc on a section 253(a) appeal stated at paragraph 16: An opinion as to impairment, be it by the trial judge or a non-expert, must meet an objective standard of ‘an ordinary citizen’, or a ‘reasonable person’ in order to avoid the uncertainties associated with subjective standards, particularly when based on inferences. To that end a list of tests and observations has been developed for use by peace officers and courts in determining whether an accused’s mental faculties and physical motor skills were impaired by alcohol to the degree of impairing the accused’s ability to operate or drive a motor vehicle. Those observations and test include: (1) evidence of improper or abnormal driving by the accused; (2) presence of bloodshot or watery eyes; (3) presence of a flushed face; (4) odour of an alcohol beverage; (5) slurred speech; (6) lack of coordination and inability to perform physical tests; (7) lack of comprehension; (8) inappropriate behaviour.