Breed and Genetics
While all dogs have a sense of smell far superior to that of humans, bloodhounds stand out even among canines. The bloodhound's scent ability has been estimated to be between 1,000 and 30,000 times as strong as that of a human being. This makes the bloodhound able to follow a scent trail that is days old and made by the walking path of a human being. These dogs can also distinguish the scent trail of one human being from that of another.
Other scenthounds, such as the Basset Hound, also have outstanding noses, but the shortness of their legs makes them less useful for tracking over long distances. Both dogs are in a family of canines that evolved to hunt by scent rather than sight.
Training
In addition to possessing an extraordinary sense of smell, bloodhounds also typically have extremely stubborn attitudes. This means that in order to take advantage of the bloodhound's abilities, the dog must be extensively trained. This training involves teaching the dog to associate treats and rewards with successful tracking according to instruction. These incentives are used to teach the dogs to use their natural abilities for tracking a person or item based on a scent article (piece of clothing or other item that has been in close contact with the query). In investigations, the dog will be given a scent item in the form of something a suspect has had close contact with or left behind at a crime scene.
The Strength of Dog Evidence
Though numerous scientific studies have proven the validity of bloodhound "testimony," this type of evidence is easily questioned in defense proceedings due to the possibility of misleading or mishandling by dog handlers. For this reason, investigators use dog tracking evidence as only one piece of a comprehensive case, or as a means to discover a likely suspect early in an investigation.
Nearly Undefeatable
The bloodhound's ability to track is nearly impossible to defeat, in spite of several urban legends about do so. In 2006, the popular Discovery Channel science show "Mythbusters" tested such tricks as sprinkling pepper, crossing a stream or river, or hiding in a tree, but found that none of these could deter a trained police tracking hound.
Tags: human being, close contact, close contact with, contact with, scent trail, sense smell