Reading some of the comments against this policy on this thread you could be forgiven for thinking that the police have just been given powers to floor the accelerator every time they see a moped and not stop until they feel like it! When they haven't have they? It's a tactic that's used when all others have failed.
Police say a combination of tactics — which also include using scrambler bikes, DNA sprays and stinger devices to deflate tyres — is reducing moped crime. Figures show 12,419 moped-related offences from January to October, compared with 19,455 in the same period last year, down 44 per cent (Evening Standard)
It's a range of tactics that are being used, and from what I understand from what I have read, making deliberate contact with a moped/bike to bring a chase to a swift end is the last resort, when all other efforts have failed.
To that end the mugger has a choice in all this, and should like everyone else, accept the concequences of the choice they make.
Choose to mug someone? Concequences are a chance of getting caught and prosecuted. Don't want those concequences? Don't mug someone.
Choose to use a moped to reduce the risk of getting caught and prosecuted?
Consequences are being asked to stop by the police, and if you do not, chased by a motorbike officer, who can go where you do, use of a stinger to deflate your tyres (would think this would probably result in parting company with the moped/bike too?) Use of DNA spray to place you at the scene, or having your (or someone else's you've stolen) moped/bike brought to a stop by a police car using contact if necessary.
Don't want to face those concequences? Then don't let it get that far!
The mugger has all the choice here, they know that if they continue to evade arrest then this will escalate the situation to a point where they may be injured by being forcibly brought to a stop. By continuing they are accepting that risk and therefore making an informed choice and are fully accountable for the choices they made to reach that point.
Why on earth should anyone who's made several choices (which are against the law) not face the concequences of their own actions?
And it's a collective decision made by the officers at the scene and the control room - this reduces the risk of adrenaline taking over because there's at least one control officer overseeing the whole operation and making a judgement call.
And with regards to a 'criminal' not being one until proven guilty in court - this tactic is about facilitating getting a suspect to court. That's what the police essentially do isn't it? They investigate crimes, identify a perpetrator(s) and arrest and detain them until they appear in court. Whether you like it or not, 'suspected criminals' are going to, on occasion, try and swerve this process to avoid the concequences. We shouldn't be removing powers from those who's job it is to enforce this process, because then we render the whole justice system useless, you could have as harsh a sentence available for a judge to hand out to a moped mugger you like, not much point if the police can't catch them in the first place is there?