Canine Substance Detection

An important aspect of a forensic investigation can be the determination of the presence and location of compounds of interest. Probably the best example is the need to establish where illicit chemicals and agricultural plants are present.

Sophisticated detection equipment such as gas and gas-liquid chromatographs can detect extremely small levels of a variety of compounds. Their portability, however, can be limited. Fortunately, the detection sensitivity of these instruments is rivaled by the nose of a dog. Dogs play a central role in some forensic operations.

Canine substance detection involves the use of specially trained dogs, commonly golden or Labrador retrievers, for the detection of illegal substances. Dogs are now being used in settings that include workplaces, airports, and schools to detect weapons, contraband, narcotic drugs, medications, beverage alcohol, firearms, and explosives.

Dogs trained to detect the scent of illegal substances are useful as they can utilize their acute sense of smell to penetrate many hiding places which are inaccessible to other detection methods. A dog has about 200 million sensitive cells in its nose, compared to approximately five million in a human being, producing a detection sensitivity that outrivals us by some 40-fold. A dog's sense of smell is made even keener by an organ in the roof of the mouth that is not found in the human olfactory system. This organ enables it to "taste" a smell, in essence amplifying a weak signal into a stronger, more easily detectable signal.

This sensitivity enables a trained dog to be able to discriminate one odor from another, even when the latter is more intense. For example, drug-sniffing dogs can be trained to detect the odors of heroin, marijuana, and cocaine even when these items are concealed in a suitcase containing perfume.

Not surprisingly, canine detection of substances like drugs is a routine part of forensic investigations aimed at curbing the illicit traffic of drugs. Canine drug detection is a common sight at areas of cross border travel such as border crossings, airports, bus stations, and ports.

Some dogs are specially trained to detect the acidic smell of nitroglycerin and the sulfur in gunpowder for work with explosives detection. Forensic investigators use arson dogs to help in criminal investigations in the aftermath of fires. These dogs locate minute traces of gas or other flammable liquids in situations where arson is suspected. Arson dogs are trained in such a way that they can accurately detect traces of chemicals at the partsper-million or even billion levels. This detection sensitivity rivals and can even exceed that achievable using electronic detectors.