One of the probable reasons in order for a judge to sign a warrant for a tap is when the safety of the United States is put to risk. This includes risks for grave attack, sabotage, or espionage.
There are several probable cause reasons that may lead a judge to sign a warrant for a wiretap, including the likelihood that the targeted individual is involved in criminal activity, the belief that the information obtained through the wiretap is relevant to the investigation, and the necessity of a wiretap for the success of the investigation. The judge must find sufficient evidence and justification to authorize such intrusion into an individual's privacy.
judge
They must provide a judge with probable cause to do a search.
A warrant is issued by a judge who is satisfied that good (probable) cause exists. Generally the only way to end a warrant is to appear.
Generally an officer must show just or probable cause to a magistrate or judge who will issue and sign a warrant.
Probable cause
In order to obtain a warrant, a police officer / prosecutor must ask a judge to issue the warrant (the application) and submit evidence (usually his own sworn testimony in the form of a written affidavit) that the search/seizure is supported by probable cause.Additional; The "application" for a warrant is called an "affidavit." The statement of probable cause contained in the affidavit MUST satisfy the issuing judge that sufficient probable cause exists to satisfy the law. ONLY after the judge signs the affidavit is a legally sufficient warrant issued.
You need a judge to issue one. You need to provide a judge with the information you are basing they need for a warrant (probable cause) and if the judge is satisfied with the information, he/she will issue the warrant.
It can depend on the type of warrant. Generally, if the the questions: who - what - where, are answered - accompanied by a short description of the probable cause presented to the judge/magistrate who approved it, that is all that is ncessary.
The officer applying for the warrant must set forth in the application that sufficient 'probable cause' exists that the person named in the warrant was the one that committed the offense. The judge reviewing the warrant application must agree that the 'probable cause' is legally sufficient to support the arrest. When he signs the application it becomes the warrant and is then returned to the officer (or agency) for service.
(in the US) Only government agents properly authorized by a judicially issued warrant have the legal authortiy to search a residence. In order to obtain such a warrant they must prepare an affidavit to present to a judge, setting forth the specific probable cause supporting the request. If the judge does not find sufficient probable cause to issue the warrant the affidavit will be denied.
In order to obtain a search warrant there has to be enough "probable cause" that a crime has been comitted or that there is information or evidence involved. This warrant is issued by a judge.
A warrant is VALIDATED by the signature of the approving judge or magistrate. An APPLICATION for a warrant must include enough information (who-what-when-where-how) and include "probable cause" that what is sworn to in the warrant is taking place within the premises named.