You do not have to be a QC for 10 years before application to the bench. You need a relevant legal qualification of 5 or 7 years. I know a local solicitor who became an extremely well respected Circuit Judge.
In a jury trial, the jury is the arbiter of fact; the Judge the arbiter of law. The Judge cannot simply "dismiss" evidence. He rules on its admissibility and can exclude evidence in certain circumstances. He can direct an acquittal for example after a successful submission of no case to answer. However, generally, the defendant is placed in the hands of the jury and it is the jury that the Prosecution has to persuade.
Personally, if New Judge advises on a criminal matter, I'd be inclined to accept that advice.