Proof of Impairment by Alcohol
The Crown need only prove any degree of impairment of the person's ability to drive, not matter how great or minor. 
Impairment refers to the physiological effect of alcohol upon the mind. This is separate from intoxication, which refers to the observable physical signs of impairment. 
Note, however, impairment is relative to a particular task. It is not simply a degree of general impairment but rather the accused's ability to drive is impaired and that the impairment is caused by alcohol or a drug. The judge should not assume that mere impairment of any functional ability is equivalent to impairment by alcohol.
Where fatigue is combined with alcohol, the only issue is whether the alcohol was a contributing factor to the impairment.
Burden and Standard of Proof
Impairment must be proven beyond a reasonable doubt.
To prove any degree of impairment of ability to drive, the crown should present evidence of aberrant driving and consumption of alcohol. If evidence of driving is not available there is greater responsibility of establishing impairment through signs of the accused.
Impairment cannot be inferred merely by the readings from the breath sample results. A judge cannot take judicial notice that a certain reading necessarily means that the person is impaired.
It is not necessary to prove that the driver intended to become impaired. Proof of the actus reus alone is sufficient to create a presumption that the accused intended to operate while impaired.
Where the evidence of impairment is equivocal on the totality of evidence, it would be dangerous to conclude beyond a reasonable doubt that there was impairment. This would include circumstantial evidence alone or equivocal evidence of impairment that shows only a “slight deviation from normal conduct”.
Circumstances and Timing of Observations
Observations of an accused made during their compelled participation in an investigation, such as during pull over investigative detention, cannot be admissible for the purpose of proving impairment as it in only admissible for proving the officer's grounds.
- R v Stellato 1993 CanLII 3375 (ON CA), (1993), 78 CCC (3d) 380 (Ont. C.A.); affirmed 90 CCC (3d) 160 (S.C.C.)
R v Brannan 1999 BCCA 669 (CanLII), (1999), 140 CCC (3d) 394, ("the test for driving while impaired contrary to s. 253(a) is any impairment")
see also R v Pijogge, 2012 NLTD(G) 94, 2012 CanLII 35597 (NL SCTD)
R v White, 2004 NLSCTD 9 (CanLII), (2004), 50 M.V.R. (4th) 177 (NLSC)
R v Loveman, 2005 NLTD 51 (CanLII), (2005), 15 M.V.R. (5th) 280 (NLSC)
R v Thompson, 2012 ONCJ 377 (CanLII) at para 13
- See R v Andrews, 1996 CanLII 6628 (AB CA),  AJ No 8 (ABCA) in the analysis section discussing this difference
- As observed in R v Raven,  O.J. No. 48 (Gen. Div.) per Durno J. at paras 47 and 50: it is incorrect to read Stellato as requiring only proof of a slight degree of impairment by alcohol as opposed to a slight degree of impairment of one’s ability to operate a motor vehicle as a result of the consumption of alcohol
- Andrews at para 17 (Courts "must not fail to recognize the fine but crucial distinction between ‘slight impairment’ generally, and ‘slight impairment of one’s ability to operate a motor vehicle.")
R v Sampson, 2009 NSSC 191 (CanLII),  NSJ No. 280
R v Christopher, (1982) BCJ No. 2008 (BCCA) at para 2-5
R v Pelletier, 1989 CanLII 4823 (SK QB), (1989) SJ No. 493 (Sask. Q.B.)
R v Payette, 1991 CanLII 1746 (BC SC), (1991) BCJ No. 795 (BCSC) at para 2 to 3
R v Barry, 1991 CanLII 2377 (BC SC), (1991) BCJ No. 2212 (BCSC), 1997 CanLII 1025 (ON CA)
R v Bartello, (1996) OJ No. 1000 (OCJ)(*no link), appeal dismissed, (1997) OJ No. 2226 (ONCA) at 22
R v Isley, 1997 CanLII 1459 (BC SC), (1997) BCJ No. 2678 (BCSC) at para 23
R v Cosentino, 2008 CanLII 68102 (ON SC), (2008) OJ No. 5263 (OSCJ) at 54, 92-93
R v Czarnecki, 2000 MBQB 42 (CanLII), 2000 Carswell Man. 215 (Q. B.)
R v Stellato, 1994 CanLII 94 (SCC),  2 S. C. R. 478
R v Polturak, Polturak, 1988 ABCA 306 (CanLII), (1988), 90 A.R. 158, 61 Alta. L.R. (2d) 306 (C.A.), at para 3
R v Beals (1956), 25 C.R. 85, 117 CCC 22 (NSCA)(*no link)
R v E. (A.L.), 2009 SKCA 65 (CanLII), 359 Sask. R. 59
R v Thomas, 2012 SKCA 30 (CanLII) at para 13
- see R v Letford, 2000 CanLII 17024 (ON CA),  O.J. No. 4841 (C.A.)
- R v Pomeroy, 2007 BCSC 142 (CanLII),  BCJ No. 170 (S.C.) at para 44
R v Mavin, 1997 CanLII 14625 (NL CA), (1997), 154 Nfld & P.E.I.R. 242, at para 37
- R v King, 1962 CanLII 16 (SCC),  SCR 746
R v Lamha, 2011 ABPC 303 (CanLII) -- impaired by a mix of drugs
- R v Peterson, 2009 ONCJ 61 (CanLII),  OJ No. 671 at 35 citing R . v Andrews, 1996 CanLII 6628 (AB CA)
- R v Phipps, 2010 ABQB 661 (CanLII)
Physical Signs of Impairment
Factors to consider include:
- erratic or abnormal driving
- blood-shot or watery eyes
- flushed face
- odour of alcoholic beverage
- slurred speech
- a deterioration of the accused’s judgement, attention, or comprehension
- a loss of motor co-ordination or control,
- increased reaction times,
- diminished sensory perceptions, or
- inappropriate or abusive behaviour
Observations of impairment:
|Odour of alcohol|| Faint
|Unusual symptoms|| none
- See R v Landes, 1997 CanLII 11314 (SK QB),  SJ 785 (SKQB) at para 16
Field Sobriety Tests
Testing for presence of alcohol or a drug
(2) If a peace officer has reasonable grounds to suspect that a person has alcohol or a drug in their body and that the person has, within the preceding three hours, operated a motor vehicle or vessel, operated or assisted in the operation of an aircraft or railway equipment or had the care or control of a motor vehicle, a vessel, an aircraft or railway equipment, whether it was in motion or not, the peace officer may, by demand, require the person to comply with paragraph (a), in the case of a drug, or with either or both of paragraphs (a) and (b), in the case of alcohol:
- (a) to perform forthwith physical coordination tests prescribed by regulation to enable the peace officer to determine whether a demand may be made under subsection (3) or (3.1) and, if necessary, to accompany the peace officer for that purpose; and
- (b) to provide forthwith a sample of breath that, in the peace officer’s opinion, will enable a proper analysis to be made by means of an approved screening device and, if necessary, to accompany the peace officer for that purpose.
R.S., 1985, c. C-46, s. 254; R.S., 1985, c. 27 (1st Supp.), s. 36, c. 1 (4th Supp.), ss. 14, 18(F), c. 32 (4th Supp.), s. 60; 1999, c. 32, s. 2(Preamble); 2008, c. 6, s. 19.
Section 254(2.1) permits the police to make a video recording of the test:
(2.1) For greater certainty, a peace officer may make a video recording of a performance of the physical coordination tests referred to in paragraph (2)(a).
Evaluation for drugs has similar requirements as 254(2) and (2.1) found in (3.1) and (3.2).