Reasonable and Probable Grounds
The legal standard of "reasonable and probable grounds" is employed in many aspects of law enforcement. It is the threshold that a peace officer must satisfy before certain powers can be employed including arrest and searches.
This level of proof is the point where "the state’s interest in detecting and preventing crime begins to prevail over the individual’s interest in being left alone at the point where credibly-based probability replaces suspicion".
Reasonable and probable grounds is the “the point where credibly-based probability replaces suspicion". It is the reasonable belief that "an event not unlikely to occur for reasons that rise above mere suspicion. "Reasonableness" concerns the legitimate expectations in the existence of certain facts. It can then be said that the belief in certain facts can be "reasonable" without being "probable".
The standard of reasonable grounds to believe is greater than mere suspicion but less than on a balance of probabilities when the totality of the circumstances are considered. It is also greater than "[m]ere suspicion, conjecture, hypothesis or ‘fishing expeditions’".
The purpose of emphasizing the "totality of the circumstances" is to "avoid concentrating on individual pieces of evidence".
The reasonableness requires that the grounds be justifiable from an objective point of view. A reasonable person placed in the position of the officer must be able to find that the grounds exist.
Reasonable grounds is a standard lower than a prima facie case and is less than a balance of probabilities.
Contrast to Reasonable Suspicion
It is higher than "reasonable suspicion", which is where "a constellation of objectively discernible facts which give the detaining officer reasonable cause to suspect that the detainee is criminally implicated in the activity under investigation"
In more recent times the standard has also been called "reasonable grounds to believe" , "reasonable belief", "reasonable probability", and to a lesser extent "probable cause". However, neither of these names have lasted.
The Charter requires that any statutory provisions enabling search and seizure must be based on "reasonable and probable grounds, established upon oath, to believe that an offence has been committed and that there is evidence to be found at the place of the search" These requirements set out the "minimum standard, consistent with s. 8 of the Charter, for authorizing search and seizure".
Reliability of Information
The officer weighing evidence to be relied up on when justifying a search or arrest must be satisfied that:
- was the information ... compelling?
- if the information is based on a tip, was the source credible?
- was the information corroborated prior to the police action?
Source of Information
Reasonable grounds need not be based on first hand knowledge. It should be based on the totality of circumstances.
When Grounds May be Challenged
In most cases, the grounds underlying police authority can only be challenged by way of a Charter application. Absent the application, the sufficiency of grounds are presumed.
Whether the judge's factual findings amount to "reasonable and probable grounds" is a question of law and is reviewable on a standard of correctness.
Hunter v Southam, 1984 CanLII 33 (SCC),  2 SCR 145, at p. 167 (cited to SCR)
R v Sanchez 1994 CanLII 5271 (ON SC), (1994), 93 CCC (3d) 357, at 367 (Ont.Ct. Gen.Div.) ("The appropriate standard of reasonable or credibly based probability envisions a practical, non-technical and common sense probability as to the existence of the facts and inferences asserted.")
R v Ngo, 2011 ONSC 6676 (CanLII) at para 35
R v Phung, 2013 ABCA 63 (CanLII) at para 11
R v Loewen  2 W.W.R. 15, 260 CCC (3d) 296 (Alta. C. A.) at para 18
Mugesera at para 114
R v Mann, 2004 SCC 52 (CanLII),  3 SCR 59 at paras 34, 41
R v Hall, 1995 CanLII 647 (ON CA), (1995), 22 O.R. (3d) 289 (C.A.) at p. 298
Loewen at para 18
n.b. which is also why certain cases use the term reasonable grounds rather than reasonable and probable grounds
- R v Le 2006 BCCA 298 (CanLII) appealed to BCCA 463 (CanLII)
- R v Sanchez at para 31
R v Slippery, 2014 SKCA 23 (CanLII), paras 21 to 22
Hunter et al v Southam Inc.
Baron v Canada, 1993 CanLII 154 (SCC),  1 SCR 416
- R v Hosie, 1996 CanLII 450 (ON CA),  O.J. No. 2175 (ONCA) at para 11
Hunter v Southam Inc. at p. 167 (SCR)
- Storrey at pp. 250-1
R v Ngo at para 35
R v Jacobson, 2006 CanLII 12292 (ONCA)
Ngo at para 35
R v Smith, 1998 ABCA 418 (CanLII) at p. 77
see R v Debot 1986 CanLII 113 (ON CA), (1986), 17 O.A.C. 141, affirmed 1989 CanLII 13 (SCC),  2 SCR 1140
Storrey at pp. 250-1 - prima facie case not necessary
R v Loewen at para 18
- Phung at para 11
Phung at para 11
R v Simpson, 1993 CanLII 3379 (ON CA), (1993), 12 OR (3d) 182 at 202
R v Jacques, 1996 CanLII 174 (SCC),  3 SCR 312 at para 24
R v Mann at para 27
Mugesera v Canada (Minister of Citizenship and Immigration), 2005 SCC 40 (CanLII) at para 114
Baron v Canada at para 42 to 44 - discussion of the difference between "reasonable grounds to believe" vs "reasonable and probable grounds"
R v Loewen,  2 SCR 167, SCC 21 (CanLII), at para 5
R v Debot,  2 SCR 1140, 1989 CanLII 13 (SCC), at p. 213
- R v Law, 2002 BCCA 594 (CanLII) at para 3, 7
- e.g. R v Chehil, 2013 SCC 49 (CanLII)
R v Morelli, 2010 SCC 8 (CanLII),  1 SCR 253, para 39
Hunter v Southam Inc., at p. 168
See also R v Vella (1984) 14 CCC 513(*no CanLII links)
R v Harris, 1987 CanLII 181 (ON CA)
- Hunter v Southam at p. 168
- Debot  2 SCR 1140, 1989 CanLII 13 (SCC) at p. 215
- R v Yorke, 1992 CanLII 2521 (NS CA), (1992), 115 N.S.R. (2d) 426 (C.A.); aff'd 1993 CanLII 83 (SCC),  3 SCR 647
- See Charter Applications
R v Dhillon, 2016 ONCA 308 (CanLII), at para 22
R v Shepherd 2009 SCC 35 (CanLII),  2 SCR 527, 309 D.L.R. (4th) 139 at para 18, 20 ("[w]hile there can be no doubt that the existence of reasonable and probable grounds is grounded in the 'factual findings' of the trial judge, the issue of whether the facts as found by the trial judge amount at law to reasonable and probable grounds is a question of law")
R v MacKenzie, 2013 SCC 50 (CanLII) at para 54
R v Feeney, 1997 CanLII 342 (SCC) at paras 30, 33, 36
R v Biccum, 2012 ABCA 80 (CanLII) at para 10
R v Nicholson, 2011 ABCA 218 (CanLII) at para 14
R v Mehari, 2011 ABCA 67 (CanLII) at paras 13-14
R v Loewen, 2010 ABCA 255 (CanLII) at para 6, aff'd 2011 SCC 21
R v Harding, 2010 ABCA 180 (CanLII) at paras 12-13
R v Abdo, 2009 ABCA 340 (CanLII) at para 5
R v Dill, 2009 ABCA 332 (CanLII) at para 4
A Context-Specific Standard
"Reasonable and probable grounds" will mean different things in different contexts.
The standard will depend on the nature of the state interest and the individual's privacy interest being intruded upon. What is "reasonable" must be "flexible if it is to be realistic and meaningful".
The officer must take into account both inculpatory as well as exculpatory evidence. Only evidence that is unreliable can be ignored. The officer must make inquiry as the circumstances reasonably permit.
In the context of a warrant search, there must be “reasonable and probable grounds, established upon oath, to believe that an offence has been committed and that there is evidence to be found at the place of the search”.
- R v Bernshaw, 1995 CanLII 150 (SCC),  1 SCR 254 (S.C.C.) at pp.304-6 per L'Heureux-Dube J.
- R v McKinlay Transport Ltd.,  1 SCR 627, 1990 CanLII 137 (SCC)
R v Ngo, 2011 ONSC 6676 (CanLII) at para 35
Ngo at para 35
R v Campbell, 2010 ONCA 588 (CanLII) at para 57 ("Considered independently each of these grounds may not have justified the authorization. However, a justice of the peace could have found from their cumulative effect that there were reasonable grounds to issue the warrant.")
R v Nguyen, 2007 ONCA 24 (CanLII) at para 4 ("The cumulative effect of the information demonstrated the existence of reasonable and probable grounds to believe that a grow operation would be found inside the house")
- Chartier v Quebec (A.G.),  2 SCR 474 1979 CanLII 17
- R v Golub at para 21
Hunter v Southam, 1984 CanLII 33 (SCC),  2 SCR 145, at p. 167 (cited to SCR)
R v Campbell, 2011 SCC 32 (CanLII), 2011 SCC 32 at para 14
Experience, Training and Knowledge of Officer
The officer may use his training and experience in determining objective reasonableness. For example, what may appear to be innocent objects to the general public may have a very different meaning to an officer experienced in drug operations This objective standard while "standing in the shoes of the police officer" has been interpreted as taking into account the officer's experience and training.
The subjective component does not require that the police officer specifically testify to having a subjective belief. It can be inferred based on the surrounding circumstances.
Assessment of reasonableness requires that the judge places themselves "in the position of the officer" and assess "the circumstances through the lens of someone who has the same experience, training, knowledge and skills as the officer".
Operating on Agency
The searching or arresting officer may rely upon the assumption that the officer directing them has the requisite grounds.
Mistaken Belief vs Reality
In assessing the reasonableness, the judge must "measure the facts as the police officer honestly understood them to be".
The subjective grounds must be based on a bona fides belief to a relevant fact. It is not necessary that the fact actually be true.
R v Biccum 2012 ABCA 80 (CanLII) at para 21
R v Lawes, 2007 ONCA 10 (CanLII) at para 4
R v MacKenzie, 2011 SKCA 64 (CanLII) at para 27, reserved (January 22, 2013)  SCCA No. 359
R v Wilson, 2012 BCCA 517 (CanLII) at paras 18-44
R v Smith, 1998 ABCA 418 (CanLII), at para 30
R v Sinclair, 2005 MBCA 41 (CanLII), at para 14
R v Messina, 2013 BCCA 499 (CanLII) - officer's experience with dial-a-dope R v Navales 2011 ABQB 404 (CanLII)
R v Sanchez
R v Rajaratnam, 2006 ABCA 333 (CanLII) at para 25
R v Kluczny, 2005 ABQB 350 (CanLII), at para 51
- R v Juan, 2007 BCCA 351 (CanLII) at paras 27-28
R v R.M.J.T., 2014 MBCA 36 (CanLII), at paras 56 to 58
R v Jacob (J.A.), 2013 MBCA 29 (CanLII) at para 35
Galye, supra at para 38 ("The assessment of whether objective grounds existed involves placing a reasonable person in the position of the officer and having that person assess the circumstances through the lens of someone who has the same experience, training, knowledge and skills as the officer. If that reasonable person would reach the same conclusion as the police officer, then the grounds for arrest will be considered to be objectively reasonable")
R v Chervinski, 2013 ABQB 29 (CanLII) at paras 21 to 22
Debot at para 50
R v Slippery, 2014 SKCA 23 (CanLII) at para 32
- Eccles v Bourque,  2 SCR 739, 1974 CanLII 191
No Ex Post Facto Analysis
Evaluation of grounds is based on what facts the officer was aware of at the time. It not relevant whether the facts, circumstances or inferences made were infact true. It is only whether it was reasonable for the officer to believe that the officer's believed facts, circumstances and inferences were reasonable.
Any evidence that comes to light after the formation of the grounds is not relevant.
The Justice of the Peace may draw "reasonable inferences" from the information found in the ITO.
"[R]easonable inference from the facts" can form the basis of reasonable and probable grounds.
An officer may search for anything "relevant or rationally connected to the incident under investigation, the parties and their culpability, that gives rise to the authorized warrant.
The standard remains the same for offences within the Code.
The officer may rely upon the observed reactions of the suspect (including body movement, posture, etc) to the presence of police.
Reliance odour alone can be problematic as the sense of smell can be "highly subjective".
The justice of the peace may take "judicial notice of concrete local circumstances in assessing the adequacy of the officer’s statement."
See R v Durling, 2006 NSCA 124 (CanLII) at paras 20, 27-28
R v Schiers,  NSJ No. 453 (C.A.)(*no CanLII links) at para 15
R v Jackson, at p. 131
Re Lubell, at p. 190
R v Sanchez, at p. 365, 370
R v Church of Scientology (No. 6), at p. 514-5
- R v Jacobson, 2006 CanLII 12292 (ON CA),  O.J. No. 1527 (Ont. C.A.), at para 22
- R v Cunsolo, 2008 CanLII 48640 (ON SC) at para 135
R v Jacob (J.A.) at para 36
R v Plummer, 2011 ONCA 350 (CanLII),  O.J. No. 2034 (C.A.) at para 23 - referring to grounds of arrest
R v Dene, 2010 ONCA 796 (CanLII), at para 4
R v Polashek (1999) 45 OR (3d) 434 (ONCA)
R v Barclay, 2018 ONCA 114 at para 36
- R v Lacelle, 2013 ONCA 390 (CanLII) at para 6
Compared to Suspicion
Where the police cannot obtain evidence without violating the Charter based only on suspicion, conjecture, hypothesis or a "fishing expedition".
The belief that the accused "may" have used a cell phone is a form of speculation and is insufficient to rely upon for an ITO targeting the phone.
R v Kokesch, 1990 CanLII 55 (SCC),  3 SCR 3 ("Where the police have nothing but suspicion and no legal way to obtain other evidence, it follows that they must leave the suspect alone, not charge ahead and obtain evidence illegally and unconstitutionally.")
R v Sanchez, 1994 CanLII 5271 (ON SC)
R v Mahmood, 2008 CanLII 51774 (ONSC)
- Mahmood, ibid.
In Search Warrants
Where the basis of the warrant relies on a confidential informer, the requirement from R v Debot must be considered. Generally, the requirement will increase "the level of verification required" where "credibility cannot be assessed", "fewer details are provided", and "the risk of innocent coincidence is greater". 
On review of a search warrant the issue is whether the evidence might reasonably be believed, not whether there is some guarantee that the infromer was telling the truth about criminal activity.
Drug Trafficking and Possession
Where an unknown person makes a "furtive visit" that is short enough to suggest drug trafficking is going on, along with informant details that drugs are being sold out of the house, is enough to form grounds that the resident is in possession of drugs.
Police cannot arrest a resident who answers the door of a marijuana grow operation without further grounds connecting the accused to the illegal activity. Please could have detained but not arrested.
Evidence of a person leaving a property, by itself, "would not be sufficient to connect that person with the crime… Believed was being committed on the property”.it follows that police cannot simply arrest everyone coming out of a residence believes to be a grow operation.
In certain contexts, seeing an accused holding a cigarette with the palm facing the front of the cigarette can be used as evidence for reasonable grounds to believe he is smoking marijuana.