Which of the following is not true with regard to arrest by a private citizen?

The assertion that private citizens may make an arrest if they have reasonable cause to believe a felony has been committed is true, as private citizens do have the authority to arrest someone they reasonably believe has committed a felony. This is based on the principle that those witnessing a serious crime, or having reasonable grounds to suspect someone has committed such an act, can take action to prevent further harm or ensure the criminal is apprehended.

In contrast, the other statements clarify the limits surrounding a citizen's authority to make arrests, particularly when it comes to misdemeanors and the necessity of having witnessed the crime. The stipulation that a private citizen may arrest for a misdemeanor only if they witnessed it is a legal safeguard to prevent wrongful arrests based on hearsay or assumption.

Therefore, the correct interpretation is that the statement indicating a citizen's authority to arrest if they merely have a belief that a felony occurred is not accurate within the options presented, making it a critical distinction in the legal landscape regarding citizen's arrests.