This article is to discuss a person who has no authority to investigate an offense can arrest a person without a warrant in flagrante delicto. This paper claims to arrest a person in flagrante delicto should be based on general awareness of committing a misdeed. "On the spot" mentioned in "Constructive Robbery" in Article 329 of the Criminal Code also could be the standard to identify whether a quasi flagrante delicto can be arrested or not. If the above two ideas are requirements of arresting a person in flagrante delicto, the status of the person arrested is not important.