Canadian Criminal Procedure and Practice/Arrest and Detention/Warrantless Arrests
Where there is no warrant for a person's arrest, a Peace Officer is governed by section 495:
Arrest without warrant by peace officer
495. (1) A peace officer may arrest without warrant
- (a) a person who has committed an indictable offence or who, on reasonable grounds, he believes has committed or is about to commit an indictable offence;
- (b) a person whom he finds committing a criminal offence; or
- (c) a person in respect of whom he has reasonable grounds to believe that a warrant of arrest or committal, in any form set out in Part XXVIII in relation thereto, is in force within the territorial jurisdiction in which the person is found.
(2) A peace officer shall not arrest a person without warrant for
- (a) an indictable offence mentioned in section 553,
- (b) an offence for which the person may be prosecuted by indictment or for which he is punishable on summary conviction, or
- (c) an offence punishable on summary conviction,
in any case where
- (d) he believes on reasonable grounds that the public interest, having regard to all the circumstances including the need to
- (i) establish the identity of the person,
- (ii) secure or preserve evidence of or relating to the offence, or
- (iii) prevent the continuation or repetition of the offence or the commission of another offence,
may be satisfied without so arresting the person, and
- (e) he has no reasonable grounds to believe that, if he does not so arrest the person, the person will fail to attend court in order to be dealt with according to law.
Consequences of arrest without warrant
(3) Notwithstanding subsection (2), a peace officer acting under subsection (1) is deemed to be acting lawfully and in the execution of his duty for the purposes of
- (a) any proceedings under this or any other Act of Parliament; and
- (b) any other proceedings, unless in any such proceedings it is alleged and established by the person making the allegation that the peace officer did not comply with the requirements of subsection (2).
R.S., 1985, c. C-46, s. 495; R.S., 1985, c. 27 (1st Supp.), s. 75.
A police officer can arrest where:
- there is reasonable grounds a person has committed an indictable offence;
- there is reasonable grounds a person is about to commit an indictable offence;
- a person is committing an indictable offence; or
- a person has a warrant out for his/her arrest.
There is limited power to arrest where the accused is found committing a summary offence and it is necessary to establish the accused's identity, among other things.
There is also a common law power for peace officers to arrest without a warrant where the officer has an honest and reasonable belief that there is a breach of the peace.
Reasonable grounds for arrest (pre-1985 was referred to as "reasonable and probable grounds') has an objective and subjective component.
Reasonable grounds is a standard lower than a prima facie case and is less than a balance of probabilities.
An arresting officer is not required the same scrutiny as a justice of a peace would need to be in conisdering a search warrant.
Police cannot arrest first and then determine after the fact whether the accused had a connection with their investigation.
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.
The officer may base his belief upon assumptions or secondary sources. However, the belief cannot be only a hunch. The circumstances must be sufficient to convince a reasonably fair-minded person put in the same position as the officer that the grounds for his or her belief are reasonable. The facts must not be considered piecemeal but in a holistic manner.
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.
A conclusory statement from one officer to another, such as “a drug transaction has taken place ”, will not support an objective finding of reasonable and probable grounds for an arrest.
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. Storrey (1990), 53 C.C.C. 316 (SCC) 
R. v. Grotheim 2001 SKCA 116 (SaskCA) 
R. v. McClelland, (1995), 165 A.R. 332 (C.A.) at para. 21
- see R. v. Debot 1986 CanLII 113 (ON CA), (1986), 17 O.A.C. 141, affirmed 1989 CanLII 13 (SCC),  2 S.C.R. 1140
- see R. v. Polashek 1999 CanLII 3714 (ON CA), (1999), 45 O.R. (3d) 434
- see R. v. Whitaker, 2008 BCCA 174, and R. v. Chaif-Gust, 2011 BCCA 528 (CanLII), 2011 BCCA 528.
- Chartier v. Quebec (A.G.),  2 S.C.R. 474 
- R. v. Golub, 1997 CanLII 6316 (ON C.A.)  at para. 21
- R. v. Chin, 2003 ABPC 118 at para. 60 
- R. v. Rajaratnam, 2006 ABCA 333 at para. 25
- R. v. Juan, 2007 BCCA 351, at paras. 27-28 
- R. v. Lal (1998), 130 C.C.C. (3d) 413 (B.C.C.A.) 
- Eccles v. Bourque,  2 S.C.R. 739 
Under s. 495(1)(b) empowers a peace officer to make a warrantless arrest where a person is "apparently" committing an offence. This must be an honestly held belief and must be reasonable. The officer does not have to be so certain as equate with a conviction.
It has been found that the strong smell of raw marijuana can be sufficient to conclude that the accused was in possession or marijuana and is arrestable under s.495(1)(b). A faint and intermittent smell is not sufficient for arrest.
- The Queen v. Biron,  2 S.C.R. 56 1975 CanLII 13
R. v. Roberge 1983 CanLII 120 (SCC), (1983), 4 C.C.C. (3d) 304
- R v Harding, 2010 ABCA 180, 482 AR 262, at para 29
A drug sniffer dog may be used to search on the basis of the lower standard of "reasonable suspicion".
- R v Kang-Brown 2008 SCC 18