In most countries the detection of crime is the responsibility of the police, though special law enforcement agencies may be responsible for the discovery of particular types of crime (e.g., customs departments may be charged with combating smuggling and related offenses). Crime detection falls into three distinguishable phases: the discovery that a crime has been committed, the identification of a suspect, and the collection of sufficient evidence to indict the suspect before a court. Many crimes are discovered and reported by persons other than the police (e.g., victims or witnesses). Certain crimes—in particular those that involve a subject’s assent, such as dealing in illicit drugs or prostitution, or those in which there may be no identifiable victim, such as obscenity—are often not discovered unless the police take active steps to determine whether they have been committed. To detect such crimes, therefore, controversial methods are sometimes required (e.g., electronic eavesdropping, surveillance, interception of communications, and infiltration of gangs).