The Metropolitan Police have been trialling the use of facial recognition in different parts of London, using cameras to scan passers-by to find matches on watch lists.
South Wales Police have used similar technology in more than a dozen trials.
Some privacy campaigners say there is no UK legislation regarding facial recognition and it is being used without regulation.
The Home Office has previously said facial recognition can be an “invaluable tool” in fighting crime.
The Metropolitan Police have now concluded the trial and are awaiting the results of an independent evaluation.
BBC Click finds out more.