Are perimeter searches without consent nor warrant ever legal?

What if it's a motor vehicle / car? Is the situation different with a house?

  • What jurisdiction is this applied in?
    – HDE 226868
    Commented May 28, 2015 at 21:37
  • @HDE226868, I think it's be interesting for US / Canada / UK / Europe.
    – cnst
    Commented May 28, 2015 at 21:46
  • 3
    It would be useful to define 'perimeter search' for those of us that have never seen that term before.
    – Flup
    Commented May 28, 2015 at 21:54
  • 2
    @Flup, in the context of a K9 traffic stop, it could be performed after you don't give consent to a search -- the dog (that's what K9, canine, stands for) would basically run around the car and scratch various parts of it, looking for probable cause for a full search etc
    – cnst
    Commented May 28, 2015 at 22:02

2 Answers 2


Huge difference between a car and a house. For example, at least in Pennsylvania no warrant is required to search a vehicle on public roads. In other states there are so many easy pretexts that you practically have little protection from a full vehicle search (although the pretext will have to withstand strict scrutiny if evidence found in a search is used to charge you with a crime).

Your house, on the other hand, still enjoys very strong fourth-amendment protections: One of my favorite U.S. Supreme Court cases on the subject is Florida v. Jardines, in which SCOTUS ruled that even approaching the front door with a drug-sniffing dog without a warrant constituted an illegal search. (The majority opinion is worth reading for its illumination of current law on this question.)

  • Hm, I don't think the Pennsylvania decision is as huge as portrayed in the media referenced. It sounds like, basically, in the old days, police could only search it if they had "visual" probable cause (or a warrant), yet now they can also rely on olfactory senses, too -- in what way is that so fundamentally different than the "visual" criteria? Even the article itself still confirms that the standard for probable cause for an actual search is still greater than for mere traffic stop alone.
    – cnst
    Commented May 29, 2015 at 7:22
  • @cnst - yes, the referenced article is a little sensationalized. The key point is that no warrant is ever needed for a LEO to legally search a stopped car. And per the PA court's opinion this appears to apply throughout the U.S.: "We adopt the federal automobile exception to the warrant requirement, which allows police officers to search a motor vehicle when there is probable cause to do so and does not require any exigency beyond the inherent mobility of a motor vehicle."
    – feetwet
    Commented May 29, 2015 at 14:10

Depends on what you mean by "perimeter search". Police can, for example, walk around the perimeter of a car or house if they have permission or the right to walk where they're walking (e.g, in your next-door neighbors' yard) If, while walking, they see evidence in your yard that you committed a crime, they can walk over and seize it (see http://www.olemiss.edu/depts/ncjrl/pdf/Law%20Enforcement%20Materials/Plain%20View%20Doctrine.pdf for more info on the plain view doctrine)

If a K9 is lawfully walking with them, and the dog smells evidence of illegal activity on your property, the police can legally act on the dog's alert.

  • 1
    Yes, plain view is a very well known doctrine. However, I wouldn't be so fast as to extend it to K9 (as evidenced by the PA.US court reference in the other answer, even the olfactory senses of the human police officers themselves weren't necessarily accepted to be within the plain view doctrine), especially if it's a house (as opposed to a car) that we're talking about.
    – cnst
    Commented Sep 10, 2015 at 23:02

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