What is the standard of proof required for probable cause?

The standard of proof required for probable cause is defined as "a fair probability." This standard reflects a threshold that is higher than reasonable suspicion but lower than the preponderance of evidence or beyond a reasonable doubt. In practical terms, probable cause exists when the facts and circumstances within an officer’s knowledge are sufficient to warrant a reasonable person to believe that a crime has been committed or that a particular individual is involved in criminal activity.

"Reasonable suspicion" is a lower standard used for initial stops or detention; it requires specific and articulable facts that criminal activity may be occurring. "Preponderance of evidence" and "beyond a reasonable doubt" are standards used primarily in civil and criminal trials respectively, where higher levels of certainty are required to determine outcomes in court. Thus, "a fair probability" accurately captures the essence of probable cause, making it the correct answer.