Making a legal arrest, gaining information for warrants, or even preventing crime can all be the result of

 The correct answer is :  surveillance

Explanation:  Before making an arrest, probable cause must be established. Surveillance, undercover tasks and raids are only used when normal methods of continuing research do not produce results. The purpose of surveillance is to obtain information about people, their activities, their companies to help solve a criminal case.

some might be scared to report the crime