Which of the following is NOT a standard of proof in criminal court?

In criminal court, the standards of proof determine the level of evidence required to establish a case. "Proof beyond a reasonable doubt" is the highest standard and is applied in criminal cases to ensure that there is a high level of certainty about the defendant's guilt before a conviction can be secured.

"Clear and convincing evidence" is a standard often used in civil cases or certain specific criminal matters such as mental competency or civil commitment proceedings. "Preponderance of evidence" is also a standard applied in civil cases, meaning that one side's evidence is more convincing than the other's.

The term "reasonable belief" is not a recognized standard of proof in criminal law. Instead, it may refer to the subjective judgment of an officer or individual based on available facts but does not meet the established legal requirements necessary to determine guilt in a criminal court. Thus, this option is the one that does not fit within the standard legal framework for assessing proof in criminal cases.