Dogs are famed for their ability to detect substances by scent. For this reason, dogs have become invaluable in the role of sniffer dogs, picking up tell-tale scent traces of illicit or banned substances from money through to drugs.

But just how good is that sense of smell and can it be confused? That's a great question to ask because it stands to reason that if a dog has a sensitive nose and you overwhelm it with input, then it may mask a more subtle smell you have a nefarious reason for wanting to hide. Such is the dilemma of asking, can dogs smell drugs through coffee? And the answer, in case the suspense is too much... is yes! 

In the same way that some people are musical, whilst others aren't, so a dog's ability to hone in and detect smells will vary. Think of it this way: A tone-deaf person can hear music and knows it's playing, but can't tell you what notes are present or the rhythm, whilst a musical person can analyze the sound and break it down into constituent parts. 

So it is with dogs and a sense of smell. Those breeds traditionally used as sniffer dogs because of their ability to distinguish subtle smells include English Springer Spaniels, Labradors, Cocker Spaniels, and Beagles. 

When on the trail of a smell, these dogs will move their heads from side to side, in order to identify where the smell is strongest. Then, they move towards it. 

Once closer to the source of the odor, the dog will slow down and inhale more deeply. This helps draw in more scent particles and allows the dog to analyze the smell more fully. 

A well-trained sniffer dog will know how to alert their handler to the presence of drugs, be they hidden in coffee or not. This can include the classic pointing stance, vigorously wagging the tail, or lying down, depending on what they have been taught to do. 

Wherever felons can make a swift buck from smuggling illicit goods, so there is a place for sniffer dogs to foil their efforts. This is done by harnessing the scent-following ability of dogs, which has been used for centuries, as tracker dogs. 

A good tracker dog was invaluable to huntsmen in times-gone-by, and could make the difference between finding and bringing down prey or starving. 

It is no coincidence that many of the dog breeds that today make great sniffer dogs come from dog breeds we associate as working dogs bred to follow a scent trail. 

However, the job description of a 'sniffer dog' is relatively new, with the first dogs being those trained to detect unexploded bombs during World War II. Their amazing ability and courage to do just this was quickly spotted as having the potential for many different applications to do with sniffing out illicit substances. 

By 1971, the United States had trained the first drug detection dogs, capable of sniffing out cocaine, marijuana, and heroin. These dogs were so successful that others were trained to detect a wider range of drugs. At this time sniffer dogs were more or less the solely employed by the government, but such was their aptitude for the task that soon private companies were training and using sniffer dogs for drugs. 

In the modern day, the Department for Homeland Security set the parameters for working sniffer dogs and is responsible for overseeing training. A typical sniffer dog will undergo around 600 to 800 hours of training before being ready to work, and then has a working life of around 6 - 8 years. 

The canine nose is around one million times more sensitive to odors than the human nose. This is down to the superior surface area of the mucosa containing scent receptors (more surface area for scent molecules to interact with) plus a larger area in the brain being dedicated to processing those signals. 

Indeed, the canine nose is designed to detect just a few scent molecules and distinguish them. The purpose of this is to help dogs communicate and know which dogs are around, how long ago they passed by, and what gender they are. This information is all obtained from subtle differences in molecules between male and female scents, and the strength of the signal. 

In reality, training a dog to smell a substance such as drugs is not difficult when you work with a dog that has the correct temperament. Hence why it is such a good question to ask if coffee can mask the smell. However, that ability of the dog to differentiate subtle odors also equips the dog to distinguish drugs from coffee. 

The principle of this training is to teach the dog to recognize the scent of drugs and then indicate to the handler they have detected the scent. Once the dog is regularly finding drugs and pointing them out, then the trainer can make the task more difficult by putting the drugs out of sight or hiding them amongst other substances. 

The first step is to teach the dog that you want them to search out drugs. To do this, use a small sample of drugs (bear in mind possession of drugs may be illegal, so this should be only done under the direction of Homeland Security). 

Place the drugs in plain sight and when the dog goes to investigate, say "Yes", in an excited voice, and give the dog a reward. Move the drugs and repeat this enthusiasm each time the dog approaches the drugs. Quickly, the dog will move directly to the drugs because they link them with getting a tasty treat or a fun game of ball. 

Once the dog is doing this regularly, label the activity with a cue word such as "Track". 

Now, place the drugs behind an object, but not so well hidden that they are difficult to find. Say "Track" and when the dog sniffs out the drugs, say "Yes!" and reward them. Again, wait until the dog is doing this with regular accuracy and then move onto the next step. 

Now, place other substances, such as coffee around the room, in addition to the drugs. When the dog sniffs the coffee, ignore them. But when they move towards the drugs, say "Yes". Again, the dog is learning they are rewarded for finding drugs but not coffee. 

Finally, hide the drugs inside a canister of coffee. This has the potential to confuse the dog, but if they learned their lessons properly, they will still detect and point out the drugs, despite the masking scent of the coffee.