Final answer:
A neutral judge or magistrate is responsible for the ultimate determination of probable cause when issuing arrest warrants. The legal requirement of probable cause is supported by the Fourth Amendment, which guards against unreasonable searches and seizures.
Step-by-step explanation:
For arrests made pursuant to a warrant, the ultimate determination that there is probable cause will be made by a neutral judge or magistrate. Probable cause is the legal threshold required for issuing an arrest warrant. It signifies that there is a reasonable basis to believe that a crime has been committed or that evidence will be found. A judge must be convinced through evidence and information provided by law enforcement that probable cause exists before issuing a warrant.
The Fourth Amendment of the U.S. Constitution protects individuals against unreasonable searches and seizures and states that no warrants shall issue, but upon probable cause, which must be supported by Oath or affirmation. This legal requirement ensures that the rights of individuals are protected unless substantial justification is provided for their infringement.
During situations where exigent circumstances exist or when evidence is in plain view, law enforcement might not need a warrant to conduct a search or an arrest. Additionally, the Supreme Court has recognized exceptions to the warrant requirement in cases where an individual does not have a 'reasonable expectation of privacy', such as searches in vehicles or during border entries.