The legality of entry gained through the use of a search warrant is dependent upon the legality of the means used to obtain the warrant. To justify the issuance of a search warrant the affiant must show the existence of probable cause.
The Role of Eyewitness Accounts in Establishing Probable Cause for the Issuance of Search Warrants,
U. Rich. L. Rev.
Available at: http://scholarship.richmond.edu/lawreview/vol5/iss2/19