All criminal cases begin with a complaint or an investigation. This usually involves someone bringing a crime to the attention of a police officer or other law-enforcement officials. The complainant is usually the victim or a witness. A police officer will be the complainant when the crime is committed in his presence. After a crime is reported, an investigation is done.
Depending on the offense and number of witnesses involved, an investigation might require several officers and forensic technicians. It might involve a large number of witnesses and physical evidence, or it may simply involve a patrol officer interviewing the alleged victim and any witnesses who are present when he arrived. Many undercover investigations span several years. They often include many hours of secretly recorded telephone conversations, undercover videotape of illegal transactions, and lots of documentary and physical evidence.
