The job of a police detective begins after a crime has been committed. Uniformed police officers are usually the first to be dispatched to the scene of a crime, however, and it is police officers who are generally required to make out the initial crime report. This report is often the material the detective uses to begin an investigation.
Detectives may also receive help early on from other members of the police department. Evidence technicians are sometimes sent immediately to the scene of a crime to comb the area for physical evidence. This step is important because most crime scenes contain physical evidence that could link a suspect to the crime. Fingerprints are the most common physical piece of evidence, but other clues, such as broken locks, broken glass, and footprints, as well as blood, skin, or hair traces, are also useful. If there is a suspect on the scene, torn clothing or any scratches, cuts, and bruises are noted. Physical evidence may then be tested by specially trained crime lab technicians.
It is after this initial stage that the case is assigned to a police detective. Police detectives may be assigned as many as two or three cases a day, and having 30 cases to handle at one time is not unusual. Because there is only a limited amount of time to devote to each case, an important part of a detective's work is to determine which cases have the greatest chance of being solved. The most serious offenses or those in which there is considerable evidence and obvious leads tend to receive priority. All cases, however, are given at least a routine follow-up investigation.
Police detectives have numerous means of gathering additional information. They contact and interview victims and witnesses, familiarize themselves with the scene of the crime and places where a suspect may spend time, and conduct surveillance operations. Detectives sometimes have informers who provide important leads. Because detectives must often work undercover, they wear ordinary clothes, not police uniforms. Also helpful are existing police files on other crimes, on known criminals, and on people suspected of criminal activity. If sufficient evidence has been collected, the police detective will arrest the suspect, sometimes with the help of uniformed police officers.
Once the suspect is in custody, it is the job of the police detective to conduct an interrogation. Questioning the suspect may reveal new evidence and help determine whether the suspect was involved in other unsolved crimes. Before finishing the case, the detective must prepare a detailed written report. Detectives are sometimes required to present evidence at the trial of the suspect.
Criminal investigation is just one area in which private detectives and investigators are involved. Some specialize, for example, in finding missing persons, while others may investigate insurance fraud, gather information on the background of persons involved in divorce or child custody cases, administer lie detection tests, debug offices and telephones, or offer security services. Cameras, video equipment, audio recording devices, and lock picks are used in compliance with legal restrictions to obtain necessary information. Some private investigators work for themselves, but many others work for detective agencies or businesses. Clients include private individuals, corporations concerned with theft, insurance companies suspicious of fraud, and lawyers who want information for a case. Whomever the client, the private investigator is usually expected to provide a detailed report of the activities and results of the investigation.
Private investigation specialties include:
- computer forensics investigators, who recover, analyze, and provide information from computers, smartphones, and other digital devices;
- legal investigators, who are hired by lawyers and law firms to help prepare criminal defenses;
- corporate investigators, who conduct internal and external investigations for corporations regarding issues such as drug abuse, sexual discrimination, and fraud and other white-collar crimes; and
- financial investigators, who gather and assess financial information on companies and individuals who would like to make a large financial transactions (such as buying a home or business, applying for a loan, etc.)
- skip tracers, who focus on locating people whose whereabouts are unknown (debt collectors are a common employer of skip tracers)
- Airport Security Personnel
- Bail Bondsmen
- Border Patrol Agents
- Bounty Hunters
- Corrections Officers
- Court Interpreters and Translators
- Court Reporters
- Crime Analysts
- Criminal Lawyers
- Customs Officials
- Deputy U.S. Marshals
- Directors of Security
- Emergency Medical Technicians
- Emergency Services Dispatchers
- FBI Agents
- Fire Inspectors
- Fire Investigators
- Fire Protection Engineers
- Fire Safety Directors
- Fire Safety Technicians
- Forensic Experts
- Forest Fire Prevention Specialists
- Fraud Examiners, Investigators, and Analysts
- Genetic Genealogists
- Intelligence Officers
- Legal Nurse Consultants
- Legal Secretaries
- Park Rangers
- Parole Officers
- Police Officers
- Polygraph Examiners
- Process Servers
- Secret Service Special Agents
- Security Consultants
- Security Guards
- Wildland Firefighters