Evidence or article search dogs are trained to locate and indicate on articles that have human scent on them.  They may be "generic" (locating articles with any human's scent) or "scent-specific" (locating articles with only one specific human's scent).  Scent-specific evidence K-9's can also be used to help confirm that a certain article was touched by a certain person.  This can be very useful when potential evidence is located by searchers.  Article search dogs must perform a "passive" indication such as a sit or down, which will not disturb the evidence.