Which of the following best describes "probable cause"?

Probable cause is defined as having reasonable grounds to believe that a crime has occurred or is about to occur. This standard is essential in the contexts of law enforcement, particularly when determining whether to execute a search warrant or make an arrest. The concept of probable cause serves as a safeguard against unreasonable searches and seizures, as it requires law enforcement to have factual evidence or reliable information that justifies their actions.

The other options do not accurately reflect the definition of probable cause. The idea of a "suspicion based on gut feeling" does not meet the requisite standard of evidence or thoroughness that probable cause demands. It requires more than mere suspicion or intuitive feelings; there must be concrete reasons to believe that a crime is involved. Furthermore, probable cause is a foundational legal principle in criminal procedure, not a legal theory used for trial defenses, which does not align with the established legal understanding. Additionally, it is incorrect to state that probable cause applies only to civil cases, as it is a critical aspect of criminal law. Thus, the appropriate characterization is indeed that it entails reasonable grounds to believe a crime has occurred.