Canadian Criminal Law/Offences/Impaired Driving and Over 80/Proof of Impairment

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Proof of Impairment by Alcohol[edit]

The Crown need only prove any degree of impairment of the person's ability to drive, not matter how great or minor. [1]

This must be proven beyond a reasonable doubt.[2]

Impairment refers to the physiological of alcohol upon the mind. This is separate from intoxication, which refers to the observable physical signs of impairment. [3]

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.[4] The judge should not assume that mere impairment of any functional ability is equivalent to impairment by alcohol.[5]

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.[6]

Impairment cannot be inferred merely by the readings from the breath sample results.[7] 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.[8] Proof of the actus reus alone is sufficient to create a presumption that the accused intended to operate while impaired.[9]

Where fatigue is combined with alcohol, the only issue is whether the alcohol was a contributing factor to the impairment.[10]

  1. R. v. Stellato 1993 CanLII 3375 (ON CA), (1993), 78 C.C.C. (3d) 380 (Ont. C.A.)[1]; affirmed 90 C.C.C. (3d) 160 (S.C.C.)
    R. v. Brannan 1999 BCCA 669, (1999), 140 C.C.C. (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
    R. v. White (2004), 50 M.V.R. (4th) 177 (NLSC)
    R. v. Loveman (2005), 15 M.V.R. (5th) 280 (NLSC)
    R. v. Thompson, 2012 ONCJ 377 at para 13
  2. R. v. Czarnecki, 2000 Carswell Man. 215 (Q. B.)
    R. v. Stellato, 1994 CanLII 94 (SCC), [1994] 2 S. C. R. 478
  3. See Andrews [1996] AJ no 8 in the analysis section discussing this difference
  4. As observed in R. v. Raven, [1999] 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
  5. R. v. Andrews [1996] AJ No 8 (ABCA) 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] N.S.J. No. 280
  6. R. v. Polturak, (1988), 90 A.R. 158, 61 Alta. L.R. (2d) 306 (C.A.), at para. 3
    Beals v. R.(1956), 25 C.R. 85, 117 C.C.C. 22 (N.S.C.A.)
    R. v. E. (A.L.), 2009 SKCA 65; 359 Sask. R. 59
    R v Thomas, 2012 SKCA 30 at 13
  7. see R. v. Letford, [2000] O.J. No. 4841 (C.A.)
  8. R. v. Pomeroy, [2007] B.C.J. 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
  9. R. v. King, 1962 CanLII 16 (SCC), [1962] S.C.R. 746
    R. v. Lamha, 2011 ABPC 303 -- impaired by a mix of drugs
  10. R. v. Christopher, (1982) BCJ No. 2008 (BCCA) at para 2-5
    R. v. Pelletier, (1989) SJ No. 493 (Sask. Q.B.)
    R. v. Payette, (1991) BCJ No. 795 (BCSC) at para 2 to 3
    R. v. Barry, (1991) BCJ No. 2212 (BCSC)
    R. v. Bartello, (1996) OJ No. 1000 (OCJ), appeal dismissed, (1997) OJ No. 2226 (ONCA) at 22
    R. v. Isley, (1997) BCJ No. 2678 (BCSC) at 23
    R. v. Cosentino, (2008) OJ No. 5263 (OSCJ) at 54, 92-93
    R. v. Comte, (2011) ABPC 131

Physical Signs of Impairment[edit]

Factors to consider include:[1]

  1. erratic or abnormal driving
  2. blood-shot or watery eyes
  3. flushed face
  4. odour of alcoholic beverage
  5. slurred speech
  6. a deterioration of the accused’s judgment, attention, or comprehension
  7. a loss of motor co-ordination or control,
  8. increased reaction times,
  9. diminished sensory perceptions, or
  10. inappropriate or abusive behaviour


  1. See R v Landes [1997] SJ 785 (SKQB) at para. 16

Equivocation of Signs[edit]

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.[1] This would include circumstantial evidence alone or equivocal evidence of impairment that shows only a “slight deviation from normal conduct”.[2]


  1. R v Peterson, [2009] OJ No. 671 at 35 citing R . v. Andrews 1996 CanLII 6628 (AB CA)
  2. Andrews, supra

Proof of Impairment by Drugs[edit]

The standard to proving impairment by drugs is the same as impairment by alcohol. The main difference involves the manner of detecting the presence of drugs and presenting evidence that there is impairment.

The investigation of an impaired by drugs case commences with the initial investigation wherein an officer forms a reasonable suspicion of impairment by drugs.

Under s. 254(2), the officer may demand that the driver submit to screening test to determine if there is reasonable grounds to believe that the driver is committing an offence under s. 253 regarding drugs.

The investigating officer will generally have a Drug Recognition Expert (or Drug Recognition Evaluator) attend the scene of the investigation to perform a Standardized Field Sobriety Test (SFST) to determine if the driver may be impaired by drugs.

If the driver presents sufficient indicia of impairment then they will be given a demand to attend the police station to undergo the full 12 step assessment as set out in the Regulations.[1]

Standardized Field Sobriety Test[edit]

The Standardized Field Sobriety Test will frequently take place at the roadside, when it is safe to do so and where the officer has not already formed the requisite grounds to believe that an offence under s. 253 has been committed.

The SFST will involve the examination of the driver's eyes for signs of Horizontal Gaze Nystagmus, a heel-to-toe walk, and a one-legged standing test.

Drug Assessment[edit]

The Drug Recognition Expert follows a 12 step assessment process that is generally uniform across all of North America.[1]

  1. Breath Alcohol Test
  2. Interview of the Arresting Officer
  3. Preliminary Examination and First Pulse
  4. Eye Examination
  5. Divided Attention Psychophysical Tests
  6. Vital Signs and Second Pulse
  7. Dark Room Examinations
  8. Examination for Muscle Tone
  9. Check for Injection Sites and Third Pulse
  10. Subject’s Statements and Other Observations
  11. Analysis and Opinions of the Evaluator
  12. Toxicological Examination

See: DRE Symptom Chart; [2]

Blood or Urine Sample[edit]

Either a blood or urine sample will be taken during or after the Drug Assessment. The purpose of the sample is largely confirmatory of the independent conclusion of the DRE on whether there is impairment.


Case Digests[edit]

  • R. v. Conron, 2012 ONCJ 171 -- DRE impaired acquittal

See Also[edit]