There are almost too many exceptions to the
warrant requirement to count; courts have acknowledged a plethora of situations
in which officers need not seek judicial approval before conducting a search. You can read about many of them here.
Searches by Private Citizens
In general, whatever a private citizen—rather than a police officer—uncovers through an
Do the Police Need a Warrant to Track You With Your Cellphone?
A “stingray” is a device the size of a suitcase that impersonates a cellphone tower. It tricks cellphones into connecting with it and in that way identifies the phones’ location.
Can a private business search your stuff, then turn it over to the police?
Question: What happens if you put your property in the hands of a private party, then that party calls the police and allows them to search it? Is the police search valid?