THE CONSTITUTION OF SCENT
It could easily be said that scent and the ability to detect it, is very important to the human race. Scent as a fragrance is a billion dollar industry and scent of a suspect is a million times a year occurrence. There are two types of sweat which is produced by the human body,
eccrine and apocrine. Eccrine sweat can occur across the entire body and are odorless. Apocrine sweat is produced around the armpits, feet and groin areas and is the source of what we call body odor. Feet can produce a stronger, 'rank' odor because it is an ideal environment for bacterial fungus to multiple because the enclosed space of socks and shoes. All of this come together to form the particular matter we call human scent. The following are websites which are more in-depth on the subject.
On the other hand, the portion to which we relate to as 'tracking scent' is inclusive of more then just a bouquet of human sweat. The aroma embodies both natural and material scents. The natural composition would include crushed particular matter where the person stepped, i.e. grass, leaves, sticks. The material composition would include some of the following.
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Clothing worn
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Shoe leather
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Shoe polish
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Perfume
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Lotions
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Hand soaps
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Laundry deterrents
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Laundry softeners
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Food odors (bacon, cheese, chips, dips, steaks)
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Diet (vegetrian, beef lover, fast foods, preservative junkie)
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Occupation ( mechanic, plumber, culinary, produce, butcher )
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Environmental factors such as where they live, i.e. oil refrinery
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Any items carrying (food or any of the above, say in a purse)
FACTORS EFFECTING SCENT
TERRAIN
Knowing the viarables which influence the existence of scent or its evaporation, is fundamentally as important as dog training itself. We know that the durability of scent depends not only climate but terrain. While most of the benchmarks such as cool weather, overcast skies or extreme heat are obvious factors, terrain is one area where personal experience will give you the best answers. I have often gained a better understanding of how scent will travel over and through different lines of the terrain by by watching videos shot during wind tunnel demonstrations showing the aerodynamic which play out when wind currents encounter solid masses. This can help you understand how scent 'pools' around obstacles such as walls or buildings, or projects itself well beyond the immediate area of the originating source, such as inside buildings or along ridge tops. Steve White, explains the concepts of scent dynamics in building searching in the article HOTWALLS which can be found at http://www.policek9.com/html/hotwall.html. Another point in the same area is residual scent which can be found in buildings, which is discussed at http://www.csst.org/residual_scent.html. Both articles illistrate the importance of understanding the provocation of scent. By understanding the scent cirriculum you can adjust your search patterns when utilizing your dog in the field.
CLIMATE
Tracking on cloudy days or late into the evening or early morning is certainly ideal but often not when you get the call. Tracking during extreme or challenging conditions is something you are striving for not something you work at once in awhile. If the dog can work under challenging heat, wind or rain, everything else is simply gravy.
One of the things which is changing the scene of K9 detective work is the ability to preserve scent something which was not even attempted 20 years ago. In the article “Survivability of Human Scent” by Stockham, Slavin and Kift they suggest that the usual standards for the preservation of scent can be stretched beyond standard definition of time. http://www.fbi.gov/hq/lab/fsc/backissu/oct2004/research/2004_10_research03.htm Many dog handlers in the United States are taught that identifiable human scent disappears after 24 hours. European studies using properly trained scent-identification dogs showed acceptable performance levels with collected scent that was aged two weeks to six months (Schoon and Haak 2002). This of course deals with scent evidence which has been collected and sealed in airtight containers. You will want to read the article "Some factors affecting human scent identification by special police dogs – preliminary results" noted below, because it came to a different conclusion.
Finally, when searching in areas where petroleum products, such as gasoline or oils are, can dimish your dog's abilities. This is actually mentioned at http://community-2.webtv.net/Hahn-50thAP-K9/K9History "the Soviets had wiith them (dogs) working in Afghanistan's hot weather, the fatigue of long journeys by armored personnel carrier (APQ), how gasoline fumes dulled the dogs' sense of smell". There are also other processes which effect smell. http://www.mold-consultants.com/myers_sniffing_dog.php?PHPSESSID=4ce12d003c629e122f47c78c621bca3e.
SCENT AS A FORM OF EVIDENCE
There is history, dating back a good hundred years of scent as a form of evidence in criminal procedings. In recent years, there has been significant attempts to refine the procedures which includes following the type of protocol which is used by the Netherland National Police, http://www.dlhp.nl/uk/ in the order of Suspect Scent Lineups. There is a book, "K9 Scent Detection" by Jan Kaldenbach as well as published articles by Jan de Bruin, "The Detection Dog and Science," or Schoon G. A. A. and J.C. De Bruin " The ability of dogs to recognize and cross-match human odours."
While each department policy will take precedence, the article Evaluating Dog Scent Evidence: Where Do I Start? gives you a starting point, which mentions these factors which may be addressed in a court of law.
- Method of scent collection
- Method of scent preservation
- Error rate assigned to particular procedure
- Error rate documented for canine used in procedure
- Canine’s training history
- Total number of scents presented
- Similarity of the scents presented
- Dog’s previous knowledge of the scents presented
- Number of identification procedure conducted
- Independence of trials; number of dogs, number of comparative traces
- Presence of a handler
If you look at the framework which has gone into some of the present suspect scent lineups, it's quite extensive and it should be. Especially given that procedures for securing the evidence have sometimes been lessen then diligent. An while it shows great promise, there are limitations which are pointed out in the article Some factors affecting human scent identification by special police dogs – preliminary results by Jezierski T., Górecka A. Institute of Genetics and Animal Breeding, Jastrzêbiec, Poland said. Police in many countries has performed identification of persons on the base of scent by specially trained dogs. A technical method for this identification is a scent line-up for matching the odour of a perpetrator collected at the crime scene to the scent sample of a person suspected. The general aim of the project was to assess the influence of various factors on the diagnostic value of scent identification by dogs as the rate of correct and false positive indications by dogs. In this part of the study the effect of individual dog, the preference (attractivity) or aversion for the scent of particular persons and the ‘freshness’ of the scent sample (storage period) were taken into account. Six experimental dogs that underwent basic and special training.
For scent identification and eight certified police dogs were taken as a research material. Altogether 11993 trials were performed. There were marked differences between dogs; the best and the worst dog indicated correctly in 72.7% and 32.1% of trials respectively, and the false positive indications occurred in 15.6% and 52.8% of trials for the best and the worst dog respectively. Less than 25% of mistakes were observed during identification of more than 95% of examined scents and therefore it was concluded that most of human scents were not ‘attractive’ for dogs. It was also found that storing the scent sample for more than 100 days resulted in decrease of correct identifications by dogs.
WEBSITES TO VISIT
| ARTICLE | WEBSITE |
|---|---|
| Evaluating Dog Scent Evidence: Where Do I Start? | http://www.nlada.org/Defender/forensics/for_lib/Documents/1120066819.33/Intro%20to%20Dog-Scent.doc |
| Scent as Forensic Evidence and its Relationship to the Law Enforcement Canine | http://www.uspcak9.com/training/forensicScent.pdf |
| Specialized Use of Human Scent in Criminal Investigations | http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research03.htm |
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