What is an essential requirement for a search warrant?

A search warrant must be supported by probable cause, which is established through an affidavit provided by law enforcement that is sworn under oath or affirmation. This requirement ensures that there is a reasonable belief that a crime has occurred and that evidence pertaining to that crime can be found in the location specified in the warrant. The use of an oath emphasizes the importance of the statement's truthfulness and maintains the integrity of the judicial process.

The other choices do not fulfill the necessary conditions for issuing a search warrant. For instance, the signature of the defendant, while potentially relevant in some contexts, does not constitute a requirement for the validity of a search warrant. Similarly, approval from a third party is not required; the law focuses on the presenting officer's testimony under the oath. Lastly, permission from local law enforcement is not required, as the search warrant itself is based on judicial authority, not departmental approval. This framework is critical in securing individuals' rights against unwarranted searches, following Fourth Amendment protections.