Reasonable Suspicion

From Criminal Law Notebook
This page was last substantively updated or reviewed January 2021. (Rev. # 89419)

General Principles

See also: Reasonable and Probable Grounds, Investigative Detention, and Plain View Search and Seizure#Sniffer Dogs

A "suspicion" refers to an expectation that a person is "possibly engaged in some criminal activity."[1]

A suspicion must be reasonable to be lawful, which requires "more than a mere suspicion and something less than a belief based upon reasonable and probable grounds". It must be supported by factual elements that can be independently assessed.[2]

Lower Than "Probable"

Reasonable suspicion is a standard lower than "reasonable and probable grounds."[3] The main distinction is "merely the degree of probability demonstrating that a person is involved in criminal activity, not the existence of objectively ascertainable facts."[4] It refers to the "possibility of uncovering criminality, not the probability of doing so."[5]

It follows that the "degree of reliability and the amount of information to establish that lower threshold is lower" than RPG.[6]


The presumption of reasonable suspicion should "not be disturbed unless it is unreasonable or not rationally capable of supporting an inference of suspicion." [7]

Taking Account of Realities of Policing

In evaluating police decision-making, the reviewing judge must "take into account that the police at the scene are often required to make quick decisions based on available information, some of which may not be complete or exact, in situations that are rapidly changing and potentially volatile."[8]

The judge should also account for an officer's experience in the particular type of investigation. The officer's experience may allow him to draw inferences and deductions that regular people would fail to make.[9] However, the court must look "carefully" at what is being claimed as "experience" and "training" to ensure that the integrity of the standard is maintained.[10]

An officer's "educated guess" cannot "supplant" the scrutiny required for reasonable suspicion standard.[11]

  1. R v Kang‑Brown, 2008 SCC 18 (CanLII), [2008] 1 SCR 456, per LeBel J, at para 75
  2. Kang-Brown, ibid., at para 75
  3. R v Xuan Nguyen, 2013 SKQB 36 (CanLII), 412 Sask R 284, per Popescul CJ, at para 27
  4. Kang‑Brown, supra, at para 75
  5. R v Navales, 2014 ABCA 70 (CanLII), 569 AR 203, per Paperny JA, at para 18
  6. Xuan Nguyen, supra, at para 27
  7. Xuan Nguyen, supra, at para 29 citing R v Gunn
    See R v Gunn, 2012 SKCA 80 (CanLII), 399 Sask.R. 170, per Caldwell JA, at paras 15 to 23
  8. Xuan Nguyen, supra, at para 30
  9. Xuan Nguyen, supra, at para 31
  10. R v Yeh, 2009 SKCA 112 (CanLII), per Richards JA, at para 53
  11. Chehil, supra, at para 47

Reasonable Suspicion Test

A reasonable suspicion lies between a mere suspicion and reasonable and probable grounds. [1]

Multitude of Conclusions Possible

Reasonable suspicion does not require that it be the only possibility, but merely one possible conclusion based on supported facts.[2] It also means that reasonable suspicion does not need to be the only inference from a particular constellation of factors.[3]

Where suspicion deals with possibilities rather than probabilities it necessarily means that it is possible to reasonably suspect that innocent people are involved in crime.[4]

Reliability and Specificity of Evidence

Reasonable suspicion can rely on information that is less reliable than for establishing "reasonable and probable grounds."[5]

The evidence forming reasonable suspicion need to indicate the "possibility of criminal behavour". The evidence itself need not include unlawful behaviour or evidence of a specific criminal act.[6]

Assessed on Totality of Evidence

The assessment is based on the totality of the evidence-all surrounding circumstances-rather than piece by piece consideration of whether the evidence is consistent with the factors. [7] The inquiry must consider "the constellation of objectively discernible facts said to give the investigating officer reasonable cause to suspect that the individual is involved in criminal activity."[8]

No Obligation to Make Inquiry

The obligation of police to consider all factors does not require them to make inquiry into exculpatory factors or rule out innocent explanations.[9]

Relevant Factors

The suspicion must be "sufficiently particularized" as an overly "generalized suspicion" would capture too many innocent persons.[10] Accordingly, factors that may "go both ways" are not sufficient on their own to support reasonable suspicion.[11] Such factors do not preclude reasonable suspicion arising when they are part of the constellation of factors.[12]

Any factors that are favourable or unfavourable (including "exculpatory, neutral or equivocal") must still be considered as part of the totality of circumstances.[13]

Standard of Review

Determination of whether factors amount to a reasonable suspicion is question of law reviewable on a standard of correctness.[14]

  1. R v Kang-Brown, 2008 SCC 18 (CanLII), [2008] 1 SCR 456, per LeBel J, at para 75
    see R v Monteyne, 2008 SKPC 20 (CanLII), 312 Sask R 242, per Kovatch J (re suspicion)
    R v Donald, 2010 SKPC 123 (CanLII), [2010] S.J. No 564, per Kalmakoff J, at para 18
  2. R v Chipchar, 2009 ABQB 562 (CanLII), (2009) AJ No 1058, per Shelley J
  3. R v Chehil, 2013 SCC 49 (CanLII), [2013] 3 SCR 220, per Karakatsanis J, at para 32
  4. Chehil, ibid., at para 28
  5. R v Kang-Brown, 2008 SCC 18 (CanLII), [2008] 1 SCR 456, [2008] SCJ No 18, per LeBel J, at para 75
  6. Chehil, supra, at para 35
  7. R v Todd, 2007 BCCA 176 (CanLII), 239 BCAC 154, per Chiasson JA
    R v Wong, 2001 BCCA 13 (CanLII), 151 CCC (3d) 155, per Braidwood JA
    R v Usher, 2011 BCCA 271 (CanLII), 307 BCAC 80, per Neilson JA
    R v Nahorniak, 2010 SKPC 68 (CanLII), 256 CCC (3d) 147, per Ottenbreit J, at para 23
    R v Cuthbertson, 2003 ABPC 83 (CanLII), 58 WCB (2d) 150, per Allen J at 46
  8. R v Navales, 2014 ABCA 70 (CanLII), 569 AR 203, per Paperny JA, at para 19
    Chehil, supra, at paras 29, 31
  9. Chehil, supra, at para 34
  10. Navales, supra, at para 19
    Chehil, supra, at paras 30 to 31
  11. Navales, supra, at para 19
    Chehil, supra, at para 31
  12. Chehil, supra, at para 31
  13. Navales, supra, at para 19
    Chehil, supra, at para 33
  14. R v Wunderlich, 2014 ABCA 94 (CanLII), 572 AR 174, per curiam, at para 8
    R v MacKenzie, 2013 SCC 50 (CanLII), 303 CCC (3d) 281, per Moldaver J, at para 54

Subjective Component

The subjective belief for the demand is a question of fact.[1]

  1. R v Bernshaw, 1995 CanLII 150 (SCC), [1995] 1 SCR 254, per Sopinka J
    R v MAL, 2003 CanLII 21523 (ON CA), [2003] OJ No 1050, per curiam
    R v Shepherd, 2009 SCC 35 (CanLII), [2009] 2 SCR 527, [2009] SCJ 35, per McLachlin CJ and Charron J, at paras 18 to 20
    R v Biccum, 2012 ABCA 80 (CanLII), [2012] AJ No 234 (CA), per curiam, at paras 9 to 10

Objective Component

Reasonable suspicion must include objective reasonableness.[1]

The judge is permitted to consider the police officer's training and personal experience in determining objective reasonableness.[2]However, the evidence of a police officer is no less worthy of scrutiny.

The officer himself cannot dictate what is reasonable and what is not. [3]

Observations of a suspect running away from police, on its own, is not enough to allow for police to detain or search.[4]

  1. R v Smith, 2011 SKPC 149 (CanLII), [2011] S.J. No 650 (Sask. Prov. Ct.), per Bobowski J, at para 44
    R v Ajula, 2011 ONCJ 10 (CanLII), per Zisman J
  2. R v Rajaratnam, 2006 ABCA 333 (CanLII), 214 CCC (3d) 547, per curiam, at para 25
    R v Juan, 2007 BCCA 351 (CanLII), 222 CCC (3d) 289, per Thackray JA, at paras 18 to 21, 222 CCC (3d) 289.
    R v MacKenzie, 2011 SKCA 64 (CanLII), 86 CR (6th) 78, per Caldwell JA
  3. R v Payette, 2010 BCCA 392 (CanLII), 259 CCC (3d) 178, per Neilson JA, at para 29
  4. e.g. R v N(N), 2009 ONCJ 508 (CanLII), per Cohen J - police see suspect running away from them in high crime area, no reason to believe crime had occurred

Compared to Reasonable Grounds

See also: Reasonable and Probable Grounds

Reasonable suspicion "involves possibilities, not probabilities."[1] Courts must be careful not to conflate the two standards.[2]

  1. R v Williams, 2013 ONCA 772 (CanLII), 111 WCB (2d) 574, per curiam, at para 22
    R v MacKenzie, 2013 SCC 50 (CanLII), 303 CCC (3d) 281, per Moldaver J, at para 38
    R v Chehil, 2013 SCC 49 (CanLII), [2013] 3 SCR 220, per Karakatsanis J, at para 27
  2. Williams, supra, at para 22
    MacKenzie, supra, at para 84
    Chehil, supra, at para 27

Impaired Driving

See also: Screening Device

A police officer may demand that a person who is found in care and control or in operation of a vehicle undergo a roadside screening test for alcohol. The officer must have "reasonable grounds" to suspect (or "reasonable suspicion") that alcohol is in their body to make a roadside test demand.[1] The quantity of alcohol and the level of impairment is irrelevant.

Burden of Proof

The burden is on the Crown to prove that there were grounds to administer the test on a balance of probabilities.

Failure to For Grounds

Where an officer administers an ASD without reasonable suspicion, a Charter violation under s. 8 and 9 result. [2]

Sufficiency of Grounds

The standard required for the ASD test under 254(3)(a)(i) is not a “standard of proof” as understood in judicial proceedings.[3]

An admission of having consumed alcohol without mention of when and how much can be considered sufficient to form a reasonable suspicion.[4]

Compelled Statements or Participation

Evidence that was obtained from the accused through his compelled participation can only be used to establish grounds of suspicion and cannot be used to incriminate the accused.[5]

  1. R v Maslanko, 2011 ABPC 202 (CanLII), per Groves J
    R v Haas, 2005 CanLII 26440 (ON CA), 200 CCC (3d) 81, per Goudge JA
    R v Church, 2008 BCSC 686 (CanLII), per Curtis J, at para 6
    R v Gaudaur, 2008 BCSC 981 (CanLII), per Romilly J, at paras 40 to 42
    R v Lemma, 2011 ABPC 312 (CanLII), per Sully J (no grounds)
    R v Beechinor, 2004 SKPC 49 (CanLII), [2004] S.J. No 187 (SKPC), per Jackson J
  2. e.g. R v Zoravkovic, 1998 CanLII 3202 (ON CA), [1997] OJ No 1010 (Ont. C.J.), per curiam
    R v Hendel, [1997] OJ No 2849 (Ont. C.J.)(*no CanLII links)
    R v Smith, [1997] OJ No 3677 (Ont. C.J.)(*no CanLII links)
    R v O’Flanagan, 2009 SKPC 14 (CanLII), [2009] S.J. No 55, per R Green J
    R v Thompson, 2003 SKPC 56 (CanLII), [2003] S.J. No 240, per Jackson J
  3. R v Loewen, 2010 ABCA 255 (CanLII), 260 CCC (3d) 296, per Slatter JA (2:1), at para 13
  4. R v Flight, 2014 ABCA 185 (CanLII), 313 CCC (3d) 442, per Veldhuis JA, at paras 39 to 61
  5. R v Orbanski; R v Elias, 2005 SCC 37 (CanLII), [2005] 2 SCR 3, per Charron J, at para 58

Reasonable Suspicion Test

The standard only requires a belief on the presence of alcohol and not the amount consumed, the effects or degree of impairment.[1]

The suspicion is of the "consumption alone and not its amount or behavioural consequences."[2]

Multiple Officers Involved

The officer who makes the demand does not need to be the officer who had initial contact with the accused.[3] However, the officer making the demand must be the one who formed a reasonable suspicion that the accused has alcohol in his system.[4] This basis can be based on information received from another officer.


The requirement of considering the totality of circumstances requires considering not only evidence suggestive of alcohol in the body but also evidence suggesting otherwise as well as the absence of evidence.

The objectively verifiable evidence should not be dissected and individually tested.[5]

Source of Alcohol

An officer should be able to describe the origin of the alcoholic smell, by indicating whether other people were in the car, or otherwise suggesting where the source of the odor could be from.[6]

It is not necessary that the crown eliminate all other possible sources of the odor of alcohol to form reasonable suspicion.[7]

Requirements for Reasonable Suspicion

For the peace officer to form reasonable suspicion, the officer must:[8]

  • subjectively and honestly suspect the driver who had alcohol in his body; and,
  • The subject of suspicion must be based on "objectively verifiable circumstances"

Reviewing the grounds requires the application of the Mackenzie test: "what a reasonable person, standing in the shoes of the investigating police officer and aware of all the objectively verifiable evidence, reasonably suspect the driver had alcohol in his or her body?"[9]

  1. R v Gilroy, 1987 ABCA 185 (CanLII), 3 WCB (2d) 79, per McClung JA
    R v Thomas, 2008 ABQB 610 (CanLII), 461 AR 216, per McDonald J
  2. Gilroy, supra, at para 8
  3. R v Telford, 1979 ABCA 244 (CanLII), 50 CCC (2d) 322, per Morrow JA
  4. R v Sahota, [2000] OJ No 3943 (ONCJ)(*no CanLII links)
    Telford, supra
  5. R v Yates, 2014 SKCA 52 (CanLII), 311 CCC (3d) 437, per Klebuc JA, at para 34
  6. E.g. Yates, ibid.
  7. Yates, ibid.
  8. Yates, ibid.
  9. Yates, ibid.

Subjective Component

There should not simply be signs of consumption of alcohol, but also signs of impaired driving skills. Once both are established, the analysis must consider the degree of each and the totality of the circumstances. [1]

Impairment to driving skills requires that on an objective basis there is impairment “such as coordination, comprehension and a poor (but not simply illegal) driving pattern.” If any one of these is found as well as evidence of alcohol consumption, then there is an objective basis to conclude the driver’s ability to drive is impaired by alcohol.[2]

Alternate explanations or imprecise descriptions do little to reduce the value of the observations. This is because the observations to not need to meet a formal burden of proof. Also, most any signs can be explained by something other than alcohol.[3]

An admission of "two drinks", without any indication of the time of these drinks, was enough to support a reasonable suspicion.[4]

An admission of “two drinks” is not relevant to establishing impairment. It is only where there is an admission of many drinks, that the inference of impairment can be made.[5]

Evidence of an amount of consumption can also be enough to create a reasonable suspicion.[6]

Grounds should include more than simply an admission of the accused that they had drank alcohol within the past three hours. [7]

  1. R v Baltzer, 2011 ABQB 84 (CanLII), 9 MVR (6th) 203, per Graesser J, at paras 40 to 41
    e.g. R v Spiry, 2010 ABPC 61 (CanLII), 25 Alta LR (5th) 181, per LeGrandeur J, at para 19 - evidence of consumption only is not likely sufficient to form reasonable grounds
  2. Baltzer, supra, at para 38
  3. Baltzer, supra, at paras 36 to 37
  4. R v Kimmel, 2008 ABQB 594 (CanLII), 459 AR 95, per Marceau J
    R v Thomas, 2008 ABQB 610 (CanLII), 461 AR 216, per J.D.B. McDonald J
    R v Ross, 2011 ABPC 173 (CanLII), AJ No 598, per Henderson J
    cf. R v Dyer, 2007 ABPC 116 (CanLII), 419 AR 296, per Fradsham J
  5. Baltzer, supra at 36-37
  6. R v Gilroy, 1987 ABCA 185 (CanLII), 79 AR 318 (CA), per McClung JA, leave to appeal to SCC refused
    R v Stauch, 2007 ABQB 85 (CanLII), 414 AR 34, per Kent J
  7. R v Mowat, 2010 BCPC 430 (CanLII), per Ellan J
    R v Baker, 2004 ABPC 218 (CanLII), [2004] AJ No 1355, per Allen J
    R v Hnetka, 2007 ABPC 197 (CanLII), [2007] AJ No 806, per Allen J
    R v Klontz, 2007 ABPC 311 (CanLII), [2007] AJ No 1283, per Anderson J
    R v Hemery, 2008 ABPC 209 (CanLII), 174 CRR (2d) 373, per Stevens-Guille J

Objective Component

The grounds need not be proven a on balance of probabilities.[1]

To be reasonable it does not need to be the only conclusion derived from the circumstances. The court considers whether a reasonable person in the circumstances would have a suspicion that the person was impaired by alcohol.

The smell of alcohol on the breath of the driver, by itself, is sufficient to support the suspicion that the driver was operating the vehicle while impaired.[2] Or the suspicion that there was alcohol in their body.[3]

However, the smell of acohol in the vehicle does satisfy the objective grounds to use the screening device.[4]

It is not necessary to consider the timing at which the suspected alcoholic beverage was consumed.[5]

The lack of evidence of consumption can weigh against the formation of a reasonable suspicion.[6]

An officer need not spell out his subjective suspicion that there is alcohol in the accused’ body using the words of s. 254(2). The court may infer the suspicion based on all of the evidence.[7]

It is generally considered that the “point in time” for the issue of reasonable grounds is at the time of the arrest. Certain cases have concerned the moment being at the time at the time of the demand.[8]

If the accused had drank alcohol within 15 minutes of the first test may render the ASD test unreliable. The mere possibility of consuming alcohol within 15 minutes does not affect the reliability of the ASD.[9] The main issue is whether there was any evidence which may have caused the officer to investigate when the accused had his last drink. If "credible evidence" exists the officer should delay test for 15 minutes to ensure reliability.[10]

  1. R v Loewen, 2010 ABCA 255 (CanLII), 260 CCC (3d) 296, per Slatter JA (2:1), at para 18
  2. R v Stauch, 2007 ABQB 85 (CanLII), AJ No 142 (QB), per Kent J
    R v Carson, 2009 ONCA 157 (CanLII), OJ No 660, per curiam
    R v Gannon, 2007 ABPC 65 (CanLII), 419 AR 137, per Semenuk J
    R v Redstar, 2009 ABPC 79 (CanLII), per Rosborough J
    R v Tellefson, 2009 ABPC 159 (CanLII), per Barley J
  3. R v Lindsay, 1999 CanLII 4301 (ON CA), [1999] OJ No 870, 134 CCC (3d) 159, per curiam
    R v Butchko, 2004 SKCA 159 (CanLII), [2004] SJ No 735, 192 CCC (3d) 552, per Cameron JA
  4. R v Rasheed, 2009 ONCJ 41 (CanLII), OJ No 631, per Bovard J, at para 20
  5. R v Aujla, 2011 ONCJ 10 (CanLII), per Zisman J, at para 36
  6. R v Zoravkovic, 1998 CanLII 3202 (ON CA), 112 OAC 119, per curiam
  7. R v Imanse, 2010 BCSC 446 (CanLII), per Crawford J
    R v Dietz, [1993] AJ No 45 (CA)(*no CanLII links)
    R v Church, 2008 BCSC 686 (CanLII), per Curtis J
    R v Donald (No.2), 2010 SKPC 123 (CanLII), 79 CR (6th) 93, per Kalmakoff J
  8. R v Shaw, 2011 SKQB 425 (CanLII), 386 Sask R 195, per Gabrielson J
  9. R v Einarson, 2004 CanLII 19570 (ON CA), 183 CCC (3d), per Doherty JA, at para 35
  10. R v Szybunka, 2005 ABCA 422 (CanLII), 380 AR 387, per Berger JA, at para 8

Sniffer Dogs

See also: Plain View Search and Seizure

"Sniffer dog" searches, most typically seen at border-crossings including airports, can be permitted on the standard of reasonable suspicion.[1]

For a sniffer dog search to be valid, the court must ask itself:[2]

  1. did the officer subjectively believe that there were reasonable grounds to suspect that the accused was in possession of the drugs?
  2. were there sufficient grounds to reasonably suspect the accused was in possession of drugs?

Reasonable suspicion in this circumstances requires an "expectation" that the accused is "possibly engaged in some criminal activity. As well, the suspicion must be supported by facts that can be subject to review."

As part of the determination of reasonable suspicion it includes the presence of a "masking agent" such as perfumes, colognes or other odour producing products. [3]

See also: R v Navales, 2011 ABQB 404 (CanLII), 520 AR 110, per Hughes J
R v Loewen, 2010 ABCA 255 (CanLII), 260 CCC (3d) 296, per Slatter JA (2:1)
R v Calderon, 2004 CanLII 7569 (ON CA), 188 CCC (3d) 481, per Laskin JA (2:1)

  1. R v Kang-Brown, 2008 SCC 18 (CanLII), [2008] 1 SCR 456, per LeBel J
  2. Kang-Brown, ibid.
  3. R v Nguyen, 2012 ABQB 199 (CanLII), 537 AR 299, per Michalyshyn J, at para 97

Drug Trafficking

Observation of someone stopping at a suspected drug house, by itself, is not sufficient to form a reasonable suspicion authorizing detention.[1] However, where the status of the house as a drug house is well-founded, a reasonable suspicion standard is sufficient.[2] Indeed, with the right circumstances, there may even be sufficient grounds to arrest.[3]

A observed hand-to-hand exchange in isolation can only amount to a suspicion and nothing more as it may equally be an innocent exchange of small objects.[4]

  1. R v Simpson, 1993 CanLII 3379 (ON CA), 79 CCC (3d) 482, per Doherty JA
  2. R v Buchanan, 2020 ONCA 245 (CanLII), per Fairburn JA, at para 31
  3. R v Rover, 2018 ONCA 745 (CanLII), 145 OR (3d) 135, per Doherty JA, at paras 11 to 13
    Buchanan, supra, at para 32
  4. R v NO, 2009 ABCA 75 (CanLII), 186 CRR (2d) 60, per curiam, at para 41
    R v Celestin, 2013 ABPC 242 (CanLII), per Fradsham J, at para 55
    R v Fares, 2014 ABQB 160 (CanLII), per Tilleman J

See Also