Requirements for the Issuance of a Search Warrant
A written search warrant must include a sworn statement of the person requesting the search called an affidavit. The affidavit includes the facts and circumstances supporting probable cause for issuing the warrant. It is made under penalty of perjury which means if a person knowing falsifies any information they could be prosecuted for perjury.
The warrant usually contains a “boiler plate” portion which includes information concerning the peace officer who signed the document. This information includes the officers’ training and experience. The purpose of including his experience and training is to demonstrate that the officer signing the warrant has sufficient expertise to offer opinions to support probable cause. The opinions of the police officer requesting the warrant are often a major portion supporting issuing the warrant. The magistrate must determine the facts and then apply the officer’s opinion, and the law, in deciding whether to sign the warrant and permit the search.
Sometimes a signed written statement is unnecessary. Penal Code section 1526(b) authorizes a sworn oral statement in lieu of a written one. The statement may be taken from the officer requesting the warrant in either of two ways: (1) the statement may be taken under penalty of perjury and recorded and transcribed or (2) the statement may be taken by fax or email.
The magistrate has the discretion, before signing the warrant, to examine under oath the person seeking the warrant and any witnesses he or she may produce. However, this is usually not done given the delay it may cause and time constraints often control the issuance of a warrant. 
The standard used to support a legal search is called “probable cause.” This standard must exist before a search can recover evidence from citizens. Whether there exists a warrant, or whether an exception to the requirement to obtain a search warrant, courts have used many descriptions of probable cause. One of the most quoted explanations of probable cause supporting a search warrant is as follows, when the facts show, “there is a fair probability that contraband or evidence of a crime will be found in a specified place,” a search is justified. 
Reasonable Expectation of Privacy
A requirement a defendant must show to challenge the legality of a search in addition to the absence of sufficient probable cause is there exists a “reasonable expectation of privacy” by the defendant to the location or object to be search. Courts in explaining this expectation have said “whether he or she has manifested a subjective expectation of privacy in the object of the challenged search that society is willing to recognize as reasonable.”  This simply means a person must show they have a legitimate reason in claiming that the area or item to be searched is subject to their control and is not open to public view or the public does not have either explicit or implicit permission to enter the location, or observe its contents.