Plain View Search and Seizure
A person has no reasonable expectation of privacy in what he knowingly exposes to the public or abandons in a public place.
A peace officer may seize any evidence which he observes by use of one or more of his senses from a lawful vantage point. If an officer is on a premises lawfully and observes items believed to be illegal, it is lawful for him to seize the items. 
For example, police may enter into a house on the basis of preserving property and the public peace, and if on entering they discover stolen property in the household, it may be considered evidence under the plain view doctrine.  Without a lawful search or lawful entrance, there can be no basis for the doctrine.
Plain view observations of only segments of an item of evidence can be sufficient to establish grounds of arrest. The officer should not move obstructions from their view.
- R v Tessling, 2004 SCC 67 (CanLII),  3 SCR 432 at para 40
R v Boersma, 1994 CanLII 99 (S.C.C.),  2 SCR 488
- R v Fitt, 1995 CanLII 4342 (NS C.A.)
R v Lauda,  2 SCR 683, 1998 CanLII 804
R v Jackson, 2005 ABCA 430 (CanLII)
- R v Shea, 1982 CanLII 2128 (ON SC), (1982), 142 D.L.R. (3d) 419 (Ont. S.C.)
R v Hébert, 1990 CanLII 3116 (QC CA), (1990), 60 CCC (3d) 422 (Que. C.A.)
R v Grenier, 1991 CanLII 3657 (QC CA), (1991), 65 CCC (3d) 76 (Que. C.A.)
R v Dreysko, 1990 ABCA 309 (CanLII), (1990), 110 A.R. 317 (Alta. C.A.)
R v Hern, 1994 ABCA 65 (CanLII), (1994), 149 A.R. 75 (Alta. C.A.)
- R v Nielsen 1988 CanLII 213, 43 CCC (3d) 548 (Sask. C.A.)
R v Bonilla-Perez, 2014 ONSC 2031 (CanLII), at para 38
R v Jones, 2011 ONCA 632 (CanLII), (2011), 278 CCC (3d) 157 at paras 56-8 (Ont. C.A.)
Plain View Doctrine
There are generally three requirements for the plain view doctrine:
- the police officer must lawfully make an initial intrusion or otherwise properly be "lawfully positioned" where he can view a particular area;
- the officer must discover incriminating evidence "inadvertently", which is to say, he may not know in advance the location of certain evidence and intend to seize it, relying on the plain view doctrine only as a pretext;
- it must be "immediately apparent" to the police that the items they observe may be evidence of a crime, contraband, or otherwise subject to seizure. These requirements having been met, when police officers lawfully engaged in an activity in a particular area perceive a suspicious object, they may seize it immediately:
Lands accessible to the public--i.e. "open fields"--do not have a reasonable expectation of privacy and so are not protected by the Charter where illegal items are found in it. However, the "open fields" doctrine does not encompass all open air private properties.
It does not stretch so far as to include a bag found in a locker at a public bus station.
Under s.489(2), where an officer is in the execution of their duties, may without a warrant, seize anything that the officer has reasonable grounds to believe is obtained by, used for, or will afford evidence towards an offence. This power is separate and apart from the common law doctrine of plain view seizure.
The plain view doctrine does not permit an officer to open a gun case to examine the contents of the case while assisting a sheriff in executing a valid eviction order.
The doctrine does not apply to circumstances where police rely upon third party reports of the contents of places otherwise protected by privacy. For example a security guard reporting the contents of a bus station locker to police.
Police returning a stolen safe cannot be said to inadvertently discover documents found within that were immediately apparent to relate to tax fraud.
The doctrine is not an exploratory search power, but rather is a seizure power.
Detecting a smell in the basement of a house an officer is lawfully in cannot justify entry into the basement without warrant on the basis of plain view.
The doctrine cannot be used to avoid the requirement of reasonable and probable grounds to search or seize evidence.
- R v Ruiz 1991 CanLII 2410 (NB C.A.), (1991), 10 C.R. (4th) 34 (N.B.C.A.)
R v Belliveau and Losier 1986 CanLII 88 (NB C.A.), (1986), 75 N.B.R.(2d) 18
R v Jones, 2011 ONCA 632 (CanLII) at para 54 - describes 4 requirements
R v Spindloe, 2001 SKCA 58 (CanLII), (2001), 154 CCC (3d) 8 (SKCA) at paras 29-37
R v Fawthrop, 2002 CanLII 45004 (ON CA), (2002), 166 CCC (3d) 97 (O.C.A.), at paras 28-34
- R v Boersma, 1994 CanLII 99 (S.C.C.)
R v Patriquen 1994 CanLII 3963, (1994), 36 C.R. (4th) 363 (NSCA); appeal dismissed on other grounds, 1995 CanLII 77,  4 SCR 42
- R v Kelly, 1999 CanLII 13120 (NB C.A.)
- R v Buhay, 2003 SCC 30 (CanLII)
- R v Makhmudov, 2007 ABCA 248 (CanLII) at para 19
- R v Stevens, 2011 ONCA 504 (CanLII),
R v Buhay per Arbour J. at para 37
R v Law,  1 SCR 227, 2002 SCC 10 (CanLII)
R v Smith (1996), 126 CCC (3d) 62 (Alta. C.A.)(*no link)
Smith, ibid. at paras 19 to 25
- Law, supra, at para 27
Officer Trespassing and Perimeter Searches
Observations should be made without violation of the law. Police making observations by trespassing at night is not permitted.
An officer may trespass upon a person's property for the purpose of communicating with the resident. They may also approach the door, knock on it and speak to anyone who chooses to speak with them.
The use of thermal imaging known as Forward Looking Infared Radar (FLIR) is not a form of search. The heat radiating from the house provides limited information about what is going on inside and virtually no information about the person core biographical information. The emanations exist on the outside of the house and so are exposed to the public.
- see R v Tessling, 2004 SCC 67 (CanLII),  3 SCR 432
The use of a sniffer dog amounts to a "search" in law. The use of the sniffer dog is almost exclusively in the realm of drug investigations.
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 (CanLII)
The police cannot seize property and then subject it to an x-ray scan without a warrant where it is not in the normal course of airport screening.
- R v Fry, 1999 CanLII 18945 (NL CA)
When police are invited into a residence they are not engaged in a search. However if they begin to look around for evidence, particularly going into dofferent rooms of the residence, that may about to a search.
- R v Choudhry, 2009 CanLII 384 (ON SC)
Statutory Seizure on Plain View
Section 489 of the Code authorizes the seizure of anything upon lawful execution of police duties or execution of a warrant: