What is the standard used to make an arrest or obtain a search warrant?

The standard used to make an arrest or obtain a search warrant is "probable cause." This legal standard is rooted in the Fourth Amendment of the United States Constitution, which protects individuals from unreasonable searches and seizures. Probable cause means that there is a reasonable basis for believing that a crime has been committed or that evidence of a crime is present in the location to be searched.

In practical terms, for law enforcement to arrest someone or to secure a warrant, they must present facts or circumstances that would lead a reasonable person to believe that a suspect has committed an offense. This standard is higher than mere suspicion, which is why “reasonable suspicion” is not sufficient for making an arrest or obtaining a warrant.

Probable cause involves a higher threshold of evidence than merely a "preponderance of evidence," which is often used in civil cases to determine the outcome of a dispute, or "clear and convincing evidence," which is a more stringent standard but is rare in criminal law. Thus, the use of probable cause ensures that there is a solid justification before law enforcement takes direct action against an individual or property.