Police detectives conduct investigation to prevent or solve criminal cases. They are experienced officers who have prior experience as patrol officers and have become familiar with procedures of protecting crime scenes, investigation, evidence gathering and preservation.They investigate crimes after police officeers have not made arrests, or they are called to crime scenes by patrol officers. They set boundaries to protect evidence from contamination or tampering. They may check victims for vital signs and get aid for medical issues if needed. They secure deceased bodies until medical examiners can conduct examinations. They obtain, mark, and protect evidence.. They locate and interview witnesses and the accused, obtain information and statements, recording or taping within legally defined parameters.Detectives record the progress of investigations, maintain written and computerized files and documentation. They report progress and perspectives to superior police personnel. They may write requests for warrants to obtain information, authorize searches or conduct arrests. They may work undercover or conduct surveillence.They testify regarding their findings in court or hearings and repond to cross-examination.They work at desks in unit offices and conduct meetings in conference areas. They spend much time in autos in th various neighborhood environments, and witness or suspect residences. They work irregular hours, are exposed to threats or injury, and may use firearms.