How are dog breeds legally defined?
<p>In the UK there are 4 breeds of dog that it is illegal to own (Pit Bull Terrier, Japanese Tosa, Dogo Argentino, Fila Brasileiro).  <a href="https://www.gov.uk/control-dog-public/banned-dogs" rel="nofollow noreferrer">The government says</a> &quot;A police or council dog expert will judge what type of dog you have&quot; and &quot;Going to court - It’s your responsibility to prove your dog is not a banned type&quot; but no information  is given about the form that this determination will take.</p>
<p><a href="https://www.dailypost.co.uk/news/north-wales-news/police-confirm-breed-dog-killed-23494566" rel="nofollow noreferrer">There is currently an example of this happening</a>, where the breed was determined to be American Bully XL (a legal breed which is a derivative of and is physically similar to the illegal Pit Bull Terrier).</p>
<p>In this day and age the most obvious solution for defining a breed is some form of genetic testing, probably with some machine learning thrown in.  In this case I would expect the rules to be well known, and hopefully published in a peer reviewed journal, and I am not aware this is the case.  Another way would a be predefined list of physical traits that could be used to define a breed, but again this could be published and made available to people who were concerned and no such list is on the government page above.</p>
<p>How are illegal breeds of dog legally defined or determined?</p>

<p>Normally, initial identification is conducted by a police <a href="https://www.cps.gov.uk/legal-guidance/dangerous-dog-offences" rel="nofollow noreferrer">Dog Legislation Officer</a>:</p>
<blockquote>
<p>...or an officer trained in dog-related legislation with a good knowledge of the identification of the prohibited types of dogs.</p>
</blockquote>
<p>Who will normally:</p>
<blockquote>
<p>provide an expedited streamlined forensic report on the dog type and will almost certainly be the prosecution expert witness. Where the police are not the prosecution’s expert witness, they will identify an expert witness from a suitable organisation...</p>
</blockquote>
<p>One such organisation is the <a href="https://www.bva.co.uk/resources-support/practice-management/dangerous-dogs-guide/" rel="nofollow noreferrer">British Veterinary Association</a>, but other expert witnesses with the requisite knowledge and understanding are available.</p>
<p>Where the defence challenge the identification / type of dog:</p>
<blockquote>
<p>the court may direct the experts to serve a statement on what they agree and what they do not agree</p>
</blockquote>
<p>Although DNA testing is possible, in my experience the identification is based around the dog's appearance and physical characteristics.</p>
<p>For example, Annex 2 of this <a href="https://www.google.co.uk/url?sa=t&amp;source=web&amp;rct=j&amp;url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69263/dogs-guide-enforcers.pdf&amp;ved=2ahUKEwjy4sbc-uj2AhVTgFwKHSuMCDEQFnoECC8QAQ&amp;usg=AOvVaw01_EdafP07j4VbFX_Svozs" rel="nofollow noreferrer">Guide(pdf)</a> gives a starting point for identifying Pit Bull Terrier (PBT) types.</p>

united-kingdom definition pets dog