When an Empty Suitcase Speaks

Blog by Stu Phillips

When an Empty Suitcase Speaks: A Lesson in Contamination and Context

This week I was working with two Customs drug detection dog teams at the airport. By day three, something happened that stopped me in my tracks — not because the dogs were wrong, but because the training environment taught us a lesson.

Setting Up the Training

My plan was to build confidence and accuracy on the luggage belt. I had asked handlers to source new or used suitcases that had not been used in training before and, importantly, had not been handled by them. The reason? To avoid contamination. I already knew that in the past the same two suitcases had been used repeatedly, which is never good practice.

We began with stainless steel odour consoles — sterilised with steam, no detergents. Five were clean, one contained 5g of cocaine. Both dogs, a Springer Spaniel and a Black Labrador, worked perfectly: clean passes on the blanks, confident indications on the target.

I should also add here that I deliberately used a relatively large quantity of cocaine for these exercises. Some trainers may argue that real-world finds are often smaller, but my priority at this stage was clarity. When working with new teams, I want to give the dogs an unmistakeable target picture: a strong, clear odour profile that leaves no doubt in their mind about what they’re searching for. Once that picture is solid, I can later reduce the amount down to trace levels. But if I start too small, I risk creating uncertainty and hesitation. Using larger amounts early on helps build confidence, accuracy, and speed — and that foundation is what later allows the dogs to perform on minute traces.

For clarification, gloves are always used when handling drug samples and they are never re-used. I go through hundreds of gloves in a training period to ensure contamination is minimised. The only items ever handled without gloves are blank training aids or equipment where I want to simulate normal handler interaction.

Next, I introduced three “new” suitcases to the belt, mixed with the consoles. Again, no issues — both dogs ignored the clean cases and responded only to the target odour.

In the third exercise, I removed the consoles and used six suitcases: five blanks and one containing 10g of cocaine zipped into a pocket. Same result: both dogs searched all cases but only indicated on the true target.

The Real Test: Blending with Live Flight Luggage

Now came the real challenge. A live flight had landed. I placed two of our training cases onto the belt airside: one empty training case (never exposed to target odour) and one containing 10g of cocaine. They were placed among approximately 100 genuine passenger suitcases.

In the arrivals hall, the Springer Spaniel worked first. It searched steadily through the stream of passenger bags. Then it reached the empty training case. Suddenly — a change of behaviour. The dog circled it, investigated repeatedly, and clearly showed the handler something was different. No final response, but noticeable enough to catch attention. Fifty cases later, the Springer found the true target case and gave a textbook trained final response (TFR).

The Black Labrador repeated the same pattern on the next flight. No reaction to the live passenger luggage, but a clear change of behaviour on the empty training case, followed by a correct TFR on the cocaine case.

What Was Going On?

The dogs were not wrong. Their changes of behaviour were telling us something important: that the “empty” training case was not neutral in their world. Despite having no target odour inside, it carried enough unique scent history — from handlers, environment, repeated exposure — to make it stand out among 100 genuine passenger bags.

I’m very conscious of contamination and cross-contamination in detection dog training. In fact, I often get criticised for being “over the top” with the controls I put in place. But this exercise is the perfect example of why I am so strict. Even with safeguards, the dogs still noticed something different about that case. That shows how easy it is for unwanted odours or handling patterns to creep into training and influence results.

Some people might ask: “If you’re so concerned about contamination, why touch any of the blank cases with bare hands at all?” It’s a fair point. My answer is simple — in the operational world, bags are always handled by people without gloves. Baggage, parcels, and cargo are touched by dozens of hands before a dog ever encounters them. If we sanitise blanks too much, we create an unrealistic picture. So, when I handle blanks barehanded, it’s not carelessness — it’s deliberate, because I want the dogs to learn that human scent is always present, and what matters is ignoring it in favour of the target odour.

When we train, every detail matters: how we store items, how we transport them, how we touch them, and even who touches them. Each of those factors can leave an odour trace that a dog will notice. If we ignore those details, we risk building false pictures into our training without even realising it.

Contamination can cause huge problems, and as we’ve just seen, even a suitcase with no target odour can create issues. If training cases are repeatedly handled, reused, or circulated without strict controls, they begin to carry their own unique scent profile. The danger is clear: we could start seeing false changes of behaviour — or even false indications — on cases that have never contained a target odour. That is a severe risk for any detection dog programme.

Over the years, I’ve worked with Customs dog units in different countries where the same training cases have been used for years. Whether those cases have contained a target odour or not, this practice is not good and should stop. Holding on to old cases is severely detrimental to the development of the dogs. Even worse, I’ve seen cases where cocaine has been placed inside a suitcase, then after use the drug sample was removed, the case sealed in an airtight bag, and labelled with the drug type, weight, and date — ready for future training. This is also not good practice. Once a case has carried a target odour, it is compromised forever.

The suitcase that held the cocaine in this exercise will never be used again. I will destroy it. Once a case has carried a target odour, it cannot go back into circulation as a “blank” — otherwise we risk teaching the dogs to search for suitcase scent history rather than the drug odour itself.

And this is where the frustration lies. I often get pushback from management when I ask for fresh training items. All they see is cost. They don’t always realise that detection dog training requires a regular supply of new or used suitcases. They don’t have to be brand new — in fact, I often source them cheaply from charity shops. But once they’ve been used with a target odour, they are finished. Saving a few pounds by reusing them is a false economy if it undermines the integrity of the dogs’ training.

The truth is, I’ve seen this before in other dog units. But seeing it happen again during this training week is what prompted me to sit down and write this blog. It’s too important to ignore. These kinds of issues don’t just fade away if we pretend they’re not there — they repeat themselves until we change the way we approach training and contamination control.

Learning Outcomes

1. Repeated use of training aids creates “training odours.” Even when “empty,” equipment can pick up unique scents that dogs learn to recognise.
2. Contamination is inevitable without strict controls. Barehanded handling, repeated exposure to the same items, or environmental residues all add up.
3. Dogs are brilliant observers of detail. If a suitcase has a unique profile, they will notice. This is not an error — it’s a reflection of their sensitivity.
4. Realism matters. Blending training items with live operational luggage revealed an issue that would never have been noticed in a sterile training setup.
5. Rotation and replacement of training equipment is essential. Once a case has carried a target odour, it must never be used as a blank again. Destruction or permanent segregation is the only option.
6. Contamination can create false problems. As seen in this exercise, even a suitcase that has never held target odour can trigger a change of behaviour. Continued use of such cases risks teaching dogs to false indicate, which can cause severe long-term issues in a detection programme.
7. Sealed storage does not make a case reusable. Placing a “used” suitcase into an airtight bag, labelling it, and bringing it back out for future training is not good practice. Once a case has contained target odour, it is compromised forever.
8. Storage, transport, and handling all matter. How training items are stored, how they’re moved, how they’re touched, and who touches them can all leave odour traces. Every stage of the process must be controlled.
9. True validation comes in operational settings. What looks fine in training may produce surprises in the real world — which is why proofing in live environments is so important.
10. Cutting costs can cut credibility. Management often resists the need for fresh training aids, but reusing contaminated equipment undermines operational reliability. Investing in a steady supply of used cases — even from charity shops — is a small price for maintaining training integrity.

Final Thought

Both dogs were correct where it mattered — finding the real target. But the exercise reminded everyone involved that detection work is not just about the dog. It’s about the environment we create for them. If we don’t manage contamination, rotation, and realism, we risk teaching the dogs to find “training cases” instead of contraband.

But here’s the question I keep asking myself: how do we set up a true test for dogs and handlers? How do we replicate the real thing? The honest answer is, it’s incredibly difficult. Just when I think I’m doing the best I can, the dogs remind me I’m still falling short — because they keep catching me out. That’s the reality of working with animals whose noses are far more powerful than our best intentions.

The two dogs I’ve been working with this week are really switched-on dogs, and they’ve reminded me just how sensitive a dog’s nose truly is. We can’t fool them. What we can do — and what we must do — is trust them. Because when we trust our detection dogs, we don’t just get results; we learn from them, and they show us exactly where our training standards need to be.

No matter how hard we try, the dogs remind us we’re still falling short — and that’s exactly why we must keep learning.