I'm aware that we are a common law country, but although there are principles in common law that Officers can do what is reasonable there are also guidelines on Police behavior are set out by PACE which is a statutory instrument designed to provide codes of practice that govern things like stop and encounter.
Your post is shot through with indications that you have a little knowledge ... and that can be a dangerous thing!
As you say, PACE governs certain things and puts limits on much that was previously ungoverned (e.g. by "Judges Rules" - common law case precedent which set some rules about how prisoners should be dealt with). But it has absolutely no impact whatsoever (other than as potentially persuasive background on how the law
may address a particular issue if called upon to rule on it) on things it doesn't cover. PACE has absolutely
no relevance I can see to the point being discussed.
Police can act when there is reasonable suspicious of an offense being committed even without common law as that is covered by statutory legislation.
Er ... that makes absolutely no sense whatsoever. If there is a statute covering the point then the Common Law is of no relevance - statute trumps common law. That is a well-established principle of the UK legal system.
People also have a right to a private life under Article 8 of ECHR, hassling everyone in an area and asking them to account for who they are and provide ID documents is in my view a violation to that right. Obviously that would be a matter for the courts to decide but unlike and most likely the police I don't assume to know what courts decide on issues.
Indeed they do. And if anyone chose to take issue with the police's proposed course of action then they could mount a challenge on that basis - either as a judicial review alleging that they are acting
ultra vires (in excess of their powers) or directly under the Human Rights legislation.
But the very same law also allows interference with that right under various circumstances:
Article 8(2) ECHR said:
"...except such as is in accordance with the law and is necessary in a democratic society in the interests of national security, public safety or the economic well-being of the country, for the prevention of disorder or crime, for the protection of health or morals, or for the protection of the rights and freedoms of others."
I, and the police, am not "assuming that [we] know what the courts decide" but we are making an informed judgment on the basis of precedent and the background to the relevant principles. On the basis of Article 8(2) and previous case decisions I am pretty sure the Courts would find what is proposed pretty proportionate and necessary (on several of the bases possible).
That is how the world works - people (police, lawyers, organisations, individuals) observe how the law is working and, taking advice if necessary, decide on how it applies to something they are planning to do. They then do it (intending to keep within the law usually) and if anyone takes issue with what they are doing they defend their approach in the Courts and see what the decision turns out to be.
Your apparent suggestion that no-one should do anything without checking with them what the Court's decision would be in advance betrays your lack of knowledge again. Firstly that would simply be impracticable - the queue would be round the block - and secondly there is no mechanism (and never has been) for the Courts deciding hypothetical cases (with the small (and irrelevant to this discussion) exception of references by the Attorney-General which provide a mechanism for the superior Courts to rule on important points of general law following a decision against the prosecution in a lower Court).
Seeing as ECHR recently ruled that collecting DNA & Fingerprints of innocent people was not ‘reasonable’ it might not automatically be the case they think collecting people’s ID is reasonable.
First, you are assuming there is some database behind the checking of ID. There is nothing to suggest that (and the reference to "open source" data suggests that police are simply cross-checking what is already there on electorol rolls, phone directories, land registry, etc. etc. rather than starting a whole new database of their own).
Secondly, you misquote the ECHR decision. They did NOT rule that collecting DNA and fingerprints of innocent people was unreasonable. They (to paraphrase) ruled that the current process (whereby the DNA and prints of suspects arrested by not charged or defendants charged but later acquitted) are
all retained
indefinitely. As a result, the government is now suggesting different periods for different categories of offence. (As a matter of fact, if you had actually read any of my previous posts on this subject, you would know that I think the decision of the ECHR decision was wrong and allows the police to keep way too many people's samples way too long.).
But this case is very different (it is being applied to all people in a location; there is no arrest (and hence no "reasonable grounds to suspect" as the starter for ten); there is no special database proposed; there is no indication of compulsion ...) and on the basis of the legal doctrine of distinguishing cases, would be decided on it's own facts, with little, if any, of the decision in the previous case being directly applied.
Especially seeing as logically I can’t see how it can actually help prevent terrorism
Now that is
very a common problem with critics of policing - substitution of "I" for "Everyone". Just because
you can't see it, or don't agree with it doesn't mean that it is not there and an open-minded and unbiased tribunal would not agree with the police's approach.
I have carefully not said that the Courts
would agree that it was a proportionate, lawful and necessary response to a situation ... but that my view is that they would.