Detection Dogs

Sometimes humans can’t do all the forensics. In the world of forensic investigations, we find an ally in a four-legged detective. Multitasking canine companions, known often as sniffer dogs, K9s, or search dogs, have become indispensable partners in the quest for truth, playing a vital role in crime scene investigations, disaster response, and even healthcare breakthroughs.

Sophisticated equipment is often expensive, unsuitable for movement, and takes long to use over large areas. Experts are often accompanied by detection dogs who aid in vital aspects of an investigation: detecting arson accelerants, explosives, drugs, human scent, cadavers, illegal agricultural goods, and infestations.

Detection dogs are most useful when the crime scene location is unknown as they can help eliminate areas from being further searched. Due to their pinpoint accuracy (a sense of smell that is 10,000 to 100,000 times sharper than ours), detection dogs can be used by crime scene investigators (CSIs) to recover samples of blood and semen.

Currently, the only other way to locate blood samples is to use Luminol, which reacts with the blood hemoglobin to create chemiluminescence. However, this only allows for blood samples to be detected under UV light when the rest of the area is completely blacked out. This makes it difficult to search exterior surfaces and “may destroy other vital evidence and innocent substances, such as household bleach” to produce false positives (Search Dogs UK). Here, detection dogs save time and money while reducing the risk of false positives as they search for a specific scent. Additionally, there is a low risk of DNA contamination as canine DNA does not react with human DNA. Canines have also been shown to “locate blood confidently up to six months old and…even as old as 24 months,” which is especially useful when locating human remains (The Conversation).

Perhaps one of the most well-known uses of police dogs is to sniff out drugs. But what propels these dogs toward the drug scent? How are they trained to detect it? In reality, the dogs believe they aren’t sniffing out a drug scent – they’re looking for their favorite toy. To associate the drug scent with the dog’s favorite toy, the trainer first hands a detection dog an unscented object – usually a white towel. At first, the dog becomes accustomed to playing with this plain towel. Eventually, drugs are wrapped in the towel, so over time the dogs come to recognize the smell of a drug to be the smell of their favorite toy. For practice, the handler will increase the difficulty of finding the toy (the towel in this case) by hiding it in harder, farther places. When the dog recognizes the drug scent, it is inclined to run toward the scent, where it will proceed to dig and scratch to retrieve the toy. Enticing the dogs with a reward, such as toys or in other cases food, encourages repetition. Slowly, different kinds of drugs are hidden in the towel so the dog is trained to recognize many drug smells. Generally, police dogs are trained to recognize illegal substances such as heroin, cocaine, marijuana, methamphetamines and chemical derivatives, MDMA, and fentanyl. In some cases, though, it is useful to have them detect the presence of legal substances, to prevent prescription abuse and drug overdose.

In the case Florida v. Harris, the Supreme Court ruled in 2013 that “drug sniffing dogs can provide the probable cause needed to allow a police officer to conduct a search,” after the Florida Supreme Court initially ruled that it was a violation of the Fourth Amendment (Larry McDougal).

Another notable use of police dogs is for detecting accelerants, or substances used to start and spread fires. They can detect low volumes of “gasoline, diesel fuel, lamp oil, paint thinner and kerosene” in precise locations that can be sent for lab analysis (Origin-and-Cause). These chemicals can further be detected in and on a variety of materials, like wood, newspaper, cardboard, plastics, rubber, linoleum, Styrofoam, carpet, cloth, and nylon. While fire accelerant lab tests cost around $400 per sample, “using an accelerant detection dog can help insurance companies improve accuracy and save money on the cost of a fire investigation” (Origin-and-Cause). However, the dogs cannot prove the commission of a crime – arson investigators and forensic scientists must work together to corroborate information to determine a crime has been committed.

During arson and drug training, “distracting odours will also be introduced, generally scents that the dog is likely to encounter during a real search” (About Forensics). In fire investigations, these distractions may include the scent of burned wood or plastic, which are not accelerants themselves. The handlers train the dogs to ignore these scents in addition to food and other toys.

Detection dogs, especially when detecting accelerants and human remains, are trained to not touch, dig through, or attempt to retrieve the remains. This is necessary for prosecutors to ensure potential evidence is not compromised or tampered with (About Forensics). This is also essential in the case of explosives detection, which could have disastrous consequences if the dogs encountered the bomb. This is when canines are trained to use a “passive alert,” such as sitting down after recognizing and moving toward a scent, rather than an “aggressive alert,” which would entail them digging through the spot wherein they detect the scent (in the case of drugs), to retrieve their toy.

To be qualified for the job, detection dogs of all kinds must pass some kind of test or get certified. When it comes to detecting firearms and explosives, detection dogs must earn an ATF (Alcohol, Tobacco, and Firearms) certification, which requires them to “successfully detect 20 different explosives odors, two of which they were never exposed to during training” (ATF).

There are 3 main kinds of trained dogs also used to detect human remains. Cadaver dogs are enlisted for recent and/or fresh remains. Historical Human Remains Detection Dogs (HHRDD) are trained in the “detection of older remains primarily through the scent of old bones and teeth” (University of Alberta). HHRDD have been used to find buried or unmarked grave sites Finally, the third kind specializes in detecting bones and burned or cremated remains (cremains). According to National Geographic, “Human cremains have a distinct odor that trained dogs can easily identify, even in a house that has been totally destroyed by a wildfire that likely topped 1,500 degrees Fahrenheit.” These detection dogs have thus been used to recover human ashes and were even used to look for traces of Amelia Earhart in a 2017 search by a Canine Forensics Unit on Nikumaroro Island.

The smell-detecting capabilities of detection dogs proved a great asset during COVID, when a 2022 study by Florida International University’s International Forensic Research Institute showed that trained dogs were also able to detect biomarkers, or “unique, volatile organic compounds,” released from the breath of COVID-infected persons. After being trained from using a scent-detection wheel, dogs were able to tell the difference between biomarkers originating from COVID-19 breath and non-COVID-19 breath accurately more than 90% of the time. In France, dogs were confirmed to have been able to identify COVID from sweat samples while in Finland, they identified COVID from skin samples.

The bond between humans and canines holds an unparalleled power to push the frontiers of science and discovery. With every successful find and every trail followed through, these sniffer dogs remind us that the age-old partnership between man and dog continues to be pivotal to solving crime in society.

Sources:

https://gfjc.fiu.edu/research/detector-dogs/#:~:text=Canines%20can%20be%20trained%20to,new%20scent%20within%20a%20month