What is Reasonable Belief?

Legal Definition
When there exists a reasonable basis to believe that a crime is being or has already been committed.
Legal Definition
a principle that a law officer can conduct a search or seize a criminal without having a warrant if he is sure a criminal act is in progress or has been committed.
Legal Definition
One begotten by attendant circumstances fairly creating it, and honestly entertained. See 110 Ala. 92, 20 South. 365.
-- Ballentine's Law Dictionary