Face recognition police tools 'staggeringly inaccurate'
&gt; Police facial recognition cameras have been trialled at events such as football matches, festivals and parades... High-definition cameras detect all the faces in a crowd and compare them with existing police photographs, such as mugshots from previous arrests.<p>&gt; &quot;When we first deployed and we were learning how to use it... some of the digital images we used weren&#x27;t of sufficient quality,&quot; said Deputy Chief Constable Richard Lewis. &quot;Because of the poor quality, it was identifying people wrongly. They weren&#x27;t able to get the detail from the picture.&quot;<p>&gt; Information Commissioner Elizabeth Denham said the issue had become a &quot;priority&quot; for her office.<p>When you roll out facial recognition technology at an event with ten thousand people and expect your magical facial recognition system to pick out just the bad guys, you quickly discover that even a system that&#x27;s 99.99 percent accurate has a 63 percent change of giving you at least one false positive in that crowd. In reality these systems are probably closer to 95 percent accurate, in which case you&#x27;re looking at <i>vastly</i> more false positives. Like hundreds per event.<p>This is the exact same statement as &quot;breast cancer screening is staggeringly inaccurate.&quot; Do you know why breast annual cancer screenings aren&#x27;t recommended for women under 40? Because breast cancer is so rare in that population that the high false positive rate outweighs the benefit of early detection. The correct thing to do is only screen <i>only if there is already a suspicion of cancer.</i><p>Similarly, pervasive surveillance where you (statistically) consider everyone a possible criminal is a waste of time. Anyone who&#x27;s ever taken a probability course will tell you that unless your facial recognition tech is fantastically accurate you&#x27;ll waste all your police officers&#x27; valuable time sorting through false positives.<p>This is not an image quality issue. It&#x27;s not a data quality issue. It&#x27;s not a deployment issue. It&#x27;s a Bayesian statistics issue. Unless your tech has superhuman 99.999% accuracy, it doesn&#x27;t matter how accurate your facial recognition is if you&#x27;re looking for a needle in a haystack. I&#x27;m sure the facial recognition is just as wonderfully accurate as breast cancer screening, it&#x27;s just being applied to a population with a stupidly rare prior.<p>This is a statistics 101, freshman undergrad-level mistake, and frankly it makes me mad as hell that authorities are stupid enough to make it and boneheaded enough to endanger their entire population&#x27;s civil liberties in the process.<p>For more info, check Wikipedia&#x27;s page on the aptly-named prosecutor&#x27;s fallacy: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Prosecutor's_fallacy" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Prosecutor's_fallacy</a>