Drug detection dogs are used by Federal, State, and local law enforcement agencies. The breed of dog used by government agencies and privately-owned K-9 training facilities for drug detection varies. Ninety percent of dogs used by U.S. Customs come from pounds across the country. In a process called selection testing, K-9 trainers look for unique behavioral patterns in dogs being considered for law enforcement work. Dogs used in drug detection must have the abilities to prey, hunt, retrieve, and follow odors and must be active and trainable. Dog handlers must possess certain psychological and physiological characteristics and must receive specialized training. One training program, Law Enforcement Training Seminars (LETS), is based in Texas but conducts classes in K-9 enforcement all over the United States. The use of sniffing dogs by the U.S. Border Patrol in Texas demonstrates their cost-effectiveness.