Dyfed-Powys' slightly more than 1,000 constables and senior officers police an area of mid- and western Wales that covers almost two-thirds of the Nation's land mass. It has the smallest budget and the lowest crime rate of any force in England and Wales. The force blurs some of the traditional distinctions between uniformed officers and detectives and between sworn officers and civilians. A number of officers, not just detectives, are trained to look for and collect fingerprints and other evidence at crime scenes. Half of the 10 specially trained crime scene officers are civilians. The mix of civilians with technical knowledge and constables with street experience maximizes the use of skills and knowledge required to solve crimes. In addition, the force relies on scientific evidence in ways that are precluded in the United States. DNA samples are taken from anyone who has committed a crime against the person, all sex offenders, all burglary offenders, and all active criminals not falling into the first three categories. Samples are also taken from all repeat offenders unless records show that DNA has previously been confirmed. A current listing of all crimes and offenders is available to all constables through the force's internal computer network. Uniformed officers rely on concerned citizens for information concerning crimes. The community's willingness to accept video surveillance to minimize disorder in public areas has been helpful. Officers are trained to give special attention to repeat victims and areas of high crime. Because officers cover the equivalent of 17,500 miles of mobile patrol each day, there is a driver training unit that provides each officer with 3 weeks of instruction during the probationary period. The force also has an air unit and a highly trained unit that operates as a combination of S.W.A.T., emergency service, and hostage negotiating units.