Last year, the USA was gripped by the Casey Anthony murder trial. Anthony was accused of murdering her daughter, Caylee, aged 2, and providing false information to the police. Caylee was not reported missing for a month, and it was a further 6 months before her decomposed remains were found in woods close to her home. When the jury reached a 'not guilty' verdict on the murder charge, the country was shocked. There had not been such a controversial verdict since OJ. I'm sure you will have your own opinions about both verdicts.
One of the prosecution witnesses at the Anthony trial was K-9 Deputy Jason Forgey, whose cadaver dog, Gerus, alerted to the scent of human remains in the trunk of Casey Anthony's car and a corner of her parents' back yard.
Watch Deputy Forgey's testimony here.
The ability of dogs to locate people and objects by scent has been utilised by law enforcement agencies for a long time. Trained dogs are used primarily for tracking, searching and locating evidence. Some dogs are cross-trained for more than one task; others are trained to perform a specific function.
There seems to be some variation in terminology for describing and differentiating between dogs trained for particular tasks, but for the purposes of this blog, I'm using the term 'Cadaver Dogs' to describe dogs which are primarily trained as search dogs, but have also received cross-training in the location of dead human bodies.
By contrast, 'Forensic Evidence Dogs' (also known as 'Human Remains Detection Dogs'), specialise in buried bodies, old homicide cases, bone searches, buildings searches, vehicle searches, crime scene searches, small scent sources and residual scent. Other forensic evidence dogs specialise in searching for firearms, explosives or drugs.
In forensic work, the breed of dog is less important than its ability to learn, interact with its handler and locate a particular scent. But a search and rescue dog, for example, needs to be robust, like a German Shepherd.
Both Cadaver Dogs and Forensic Evidence/HRD Dogs are trained to locate the scent of death, which is caused by chemical decomposition. However, because they are not cross-trained, Forensic Evidence/HRD Dogs are never looking for live scent. They have been taught to exclude fresh human scent and to ignore all animal scents, whether fresh or decomposed, when carrying out a search.
Working slowly and methodically, a fully trained Forensic Evidence/HRD Dog will not disturb a crime scene nor will it retrieve evidence. It will also search homes and vehicles without causing any damage. When it finds a residual scent of a dead human or dried blood, for example, it will alert its handler by demonstrating a particular behaviour, such as standing still and barking, or lying down.
The scent may not indicate the actual location of the remains. Running water can move the scent away from the grave site. So although the dog will alert where the scent is strongest, this may be some distance from the body itself.
The handler of a Forensic Evidence/HRD Dog also has to be highly trained. If called to court, the handler has, in effect, to testify on behalf of their dog. So handlers log all their dogs' training and also take courses in orienteering, criminal procedures, report writing, hazardous materials awareness and canine first aid.
So how accurate are Cadaver Dogs and Forensic Evidence/HRD Dogs? Canine fallibility was alluded to in Deputy Forgey's cross-examination.
Various studies have shown that handler error and inexperience can lower the recovery success rate from 100% to as little as 57%. It doesn't matter how good the dog is at locating evidence, if the handler is unable to interpret the dog's alerts properly.
Just like a human, a tired, hungry or stressed dog will not perform as well as when it is fresh, fed and happy. In fact, a severely fatigued dog may give a false alert, simply because it wants to rest.
Forensic Evidence/HRD Dogs are also employed away from law enforcement work. The Institute for Canine Forensics has been using Forensic Evidence/HRD Dogs to search for Native American burials and cremations on the site of the proposed Tule Wind Energy site in the McCain Valley, California.
Here is a video of one of the dogs at work.
Don't forget, you can find out when I post a new blog - and much more - by following me on Twitter @forensicswrite.
Watch Deputy Forgey's testimony here.
The ability of dogs to locate people and objects by scent has been utilised by law enforcement agencies for a long time. Trained dogs are used primarily for tracking, searching and locating evidence. Some dogs are cross-trained for more than one task; others are trained to perform a specific function.
There seems to be some variation in terminology for describing and differentiating between dogs trained for particular tasks, but for the purposes of this blog, I'm using the term 'Cadaver Dogs' to describe dogs which are primarily trained as search dogs, but have also received cross-training in the location of dead human bodies.
By contrast, 'Forensic Evidence Dogs' (also known as 'Human Remains Detection Dogs'), specialise in buried bodies, old homicide cases, bone searches, buildings searches, vehicle searches, crime scene searches, small scent sources and residual scent. Other forensic evidence dogs specialise in searching for firearms, explosives or drugs.
In forensic work, the breed of dog is less important than its ability to learn, interact with its handler and locate a particular scent. But a search and rescue dog, for example, needs to be robust, like a German Shepherd.
Both Cadaver Dogs and Forensic Evidence/HRD Dogs are trained to locate the scent of death, which is caused by chemical decomposition. However, because they are not cross-trained, Forensic Evidence/HRD Dogs are never looking for live scent. They have been taught to exclude fresh human scent and to ignore all animal scents, whether fresh or decomposed, when carrying out a search.
Working slowly and methodically, a fully trained Forensic Evidence/HRD Dog will not disturb a crime scene nor will it retrieve evidence. It will also search homes and vehicles without causing any damage. When it finds a residual scent of a dead human or dried blood, for example, it will alert its handler by demonstrating a particular behaviour, such as standing still and barking, or lying down.
The scent may not indicate the actual location of the remains. Running water can move the scent away from the grave site. So although the dog will alert where the scent is strongest, this may be some distance from the body itself.
The handler of a Forensic Evidence/HRD Dog also has to be highly trained. If called to court, the handler has, in effect, to testify on behalf of their dog. So handlers log all their dogs' training and also take courses in orienteering, criminal procedures, report writing, hazardous materials awareness and canine first aid.
So how accurate are Cadaver Dogs and Forensic Evidence/HRD Dogs? Canine fallibility was alluded to in Deputy Forgey's cross-examination.
Various studies have shown that handler error and inexperience can lower the recovery success rate from 100% to as little as 57%. It doesn't matter how good the dog is at locating evidence, if the handler is unable to interpret the dog's alerts properly.
Just like a human, a tired, hungry or stressed dog will not perform as well as when it is fresh, fed and happy. In fact, a severely fatigued dog may give a false alert, simply because it wants to rest.
Forensic Evidence/HRD Dogs are also employed away from law enforcement work. The Institute for Canine Forensics has been using Forensic Evidence/HRD Dogs to search for Native American burials and cremations on the site of the proposed Tule Wind Energy site in the McCain Valley, California.
Here is a video of one of the dogs at work.
Don't forget, you can find out when I post a new blog - and much more - by following me on Twitter @forensicswrite.
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