Re: Why do the words...
" "Although a positive identification is not enough evidence to result in a conviction" "
But it will arouse suspicion about a person.
As the then Home Secretary David Blunkett once said "No one who is innocent has anything to fear from a police investigation of them". One of his ideas was that everyone's PC's contents should be liable to random checks - and buying a child an ice-cream should trigger an investigation. One of his political opponents said "David believes everyone should be in prison who isn't David Blunkett".
Unfortunately the police do tend to stick with the first idea that appeals to them. The cleaner the suspect - the more convinced they become that they are "guilty - but very clever".
They seem to have a tendency these days to arrest "on suspicion of...." - then use the automatic power of search to disrupt a person's life in the hope of finding something that might look incriminating.
Presumably the large database of pictures of people attending peaceful demonstrations etc will be off limits to them? So too - passport, driving licence pictures? Full face pictures are needed - like those taken by the helmet cameras that are being mooted? "Good afternoon sir - we just record these conversations for your safety - your name is?".
It won't take long before the database is like DNA samples - automatic and very hard for innocent people to get removed "because it is potentially so useful". Once it gets large then false positives are going to become normal.