What is preventive arrest?

Answer 1

A preventive arrest is when the police arrest an individual or group of individuals to prevent the occurrence or probable occurrence of a crime. Preventive arrest is still, I believe, illegal in the U.S., though it is practiced in other countries. For example: suppose Alan is extremely angry with Bob, who is not present but Alan knows where Bob lives/is at the time. Alan has a history of violent behavior and is known to own a number of guns. Alan believes Bob has wronged him in some way and is heard to make the statement, "Somebody ought to get that guy". A police officer might make a preventive arrest on Alan in order to prevent Alan from doing harm to Bob, even though no crime has yet been committed and there is as yet no evidence that a crime is about to be committed.