How To Conduct a Bloodhound Line-up

It’s always fascinating to me when I run into detectives who don’t know, or have never conducted, a bloodhound line up. So, I figured if they weren’t aware of them you might not be either. As a breed, there is no better tracking dog than the Bloodhound in my opinion. They have been bred for centuries and valued by Kings and cops alike for their tracking prowess. I have written before about how they can track under challenging conditions.  Bloodhounds are said to be able to detect scent in parts per million which means they need very little scent to follow effectively. In fact, I’ve had cases where these dogs can follow people in cars! You almost have to see it to believe it. When you consider how well this breed can track it should come as no surprise that they could be used in a line-up scenario.

The theory is pretty straight forward. If a dog can track a person to a particular location (to the exclusion of other people whose scent has also transected the trail) then they should be able to pick out the source of that scent from a group of similar “looking” sources. This line-up can be done with people or vehicles to identify the scent of a suspect, victim, or decomposing scent. What scent you are searching for will dictate how you set up the search. For example, if you are looking for the scent of a little girl that was abducted in a suspect vehicle you would scent the dog (let the dog sniff something containing the girls scent like a piece of her clothing) on something from her. If you were looking for a suspect scent you’d scent the dog off of him or something containing his scent. In fact, handlers will often let the dog sniff the law enforcement investigators on scene so that the dog knows to ignore those scents while searching for evidence.  So having said that, how do we conduct a line-up?

Let’s say we’re doing a line up with the suspect vehicle.  While dog’s don’t know what car the suspect was driving by model (even the best bloodhound doesn’t know the difference between a 1963 Corvette and a 1968 Camaro) investigators usually try to assemble six to eight vehicles of similar style tot he suspect vehicle. With common cars we usually ask a rental agency or dealership for “filler” vehicles. We might also use personal vehicles from officers if they match. So if your suspect is driving a 2007 Nissan Pathfinder we’d try to find vehicles that would match or come very close to it (like a Toyota Fourrunner).  Investigators will choose a “scent neutral” site for the line up. This might be a parking lot or impound lot which is not associated with the suspect or victim on a regular basis. For example, you wouldn’t want to do the line-up at the suspect’s home or place of work. The vehicles are parked all facing the same direction and spaced about 10 to 15 yards apart. The dog and handler are not present and the handler won’[t know which car belongs to the suspect. This is to avoid any possible claim that the handler somehow coached the dog to the correct car.

The handler will scent the dog off an article of clothing from the victim. This is done in a location which is out of site from the line-up. It might be several blocks away if in a city area or 1/4 mile away if in a very rural setting.  The dog is then allowed to track towards the line-up area. As the dog approaches the vehicles he/she will inspect each vehicle one by one. Every well trained dog will have a “signal” that tells the handler the dog has found the scent. Usually this signal is obvious and not something that could be misconstrued. A dog will have only one signal. Most dogs I have worked with signal a “hit” by sitting down. Others might stop a track and return to the handler first before sitting. Investigators are told ahead of time what that signal will be so they can recognize it if the dog hits on the suspect vehicle (because the investigators know which vehicle belongs to the suspect).  Even if the dog hits on the first vehicle the handler will make them inspect each one. Oftentimes investigators will videotape the line-up so it can be shown later to the jury or judge during trial.

These line-ups are really fun to watch. If you want to put one in your novel you could use one for vehicles or people. Feel free to get a little creative in what scents your characters are looking for.