From tracking criminals to sniffing out drugs, dogs have long helped police crack cases. Now experts are hoping a database of canine DNA could offer vital leads. While hair, saliva and other canine material may be found at crime scenes, or on individuals connected to incidents, scientists say they are often not fully investigated.
Yet such traces could provide valuable clues, from the identity of a canine perpetrator to evidence a dog’s owner was present at a crime scene. We live with dogs all the time. And so if you can identify canine material associated with a crime like that, then that can be very powerful in being able to provide intelligence to help solve a human case where there’s no other evidence.” As a result, researchers at King’s College London and the Royal Veterinary College have teamed up to harness the potential of canine DNA.
This technique involves looking at the number of times these small segments are repeated in the DNA, resulting in two numbers for each STR – one inherited from each parent. Syndercombe Court noted the set of numbers provided a virtually unique profile – be it for a human or a dog. What is more, in dogs some sets of numbers are more common in some breeds than others.
By focusing on STRs the team has built a database covering 80 different breeds – the first of its kind in the UK. For the 10 most common breeds, including labradors, cocker spaniels and miniature schnauzers, samples were taken from at least 50 dogs of each breed. The upshot is that canine DNA from a crime scene can be analysed and the results either compared with those from a particular dog – allowing that animal to be confirmed or ruled out as being linked to a crime – or screened against the database, potentially allowing experts to identify the breed of dog from which it came.
The latter could be particularly useful where the dog thought to be linked to a crime is unknown, or where samples cannot be taken from a canine suspect, or where the sample does not match the DNA of a dog under suspicion. Syndercombe Court said her team now hoped to expand their database to include breeds such as pitbull terriers, American XL bullies and Japanese tosas that are banned in the UK. While the STR analysis focuses on DNA from the nucleus of a cell, the team have also created a database using another approach: sequencing DNA from within mitochondria – the tiny structures that power cells.
With many mitochondria per cell, this approach can be useful where there is very little material to work with – although it is more limited as this DNA is only passed from mother to offspring. The focus on doggy DNA has already offered insights for police investigations. In one case, the approach shed light on whether serious injuries sustained by a man were down to another person – as he claimed – or occurred when he tripped over his own dogs as they attacked the accused.
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