The selection process for a police canine includes a number of “character traits” and physical attributes depending on the role of the animal. For example, patrol dogs must be able to apprehend a criminal suspect on command whereas a Drug Detector Dog is trained very differently. Drug dogs need to be able to perform what is called “passive indication” so that they do not damage private property. This type of training also helps the drug dog to go unnoticed by a suspect. The METRO/SWAT K-9 Unit may train canines in for more than one discipline. While patrol is the primary discipline, dogs may also be trained for explosives or drug detection.