In criminal law, what does "probable cause" refer to?

The term "probable cause" is specifically defined as the standard of evidence necessary to justify an arrest or to issue a search warrant in criminal law. It reflects a level of suspicion that is more substantial than mere speculation or hunches, but less than the level of certainty required for a conviction.

In the context of criminal law, probable cause requires that law enforcement have sufficient facts and circumstances that would lead a reasonable person to believe that a crime has been or is being committed, or that evidence of a crime will be found in the location to be searched. This standard is foundational in ensuring that individuals' rights are protected from unreasonable searches and seizures, as guaranteed by the Fourth Amendment of the United States Constitution.

The other choices pertain to different legal concepts: the requirement for appeal in higher courts relates to legal grounds for seeking appellate review, reasonable suspicion is a lesser standard used specifically for stops and frisks rather than for arrests or searches, and the burden of proof in civil cases typically pertains to the "preponderance of the evidence" standard, which is distinct from the criminal standard of beyond a reasonable doubt.