Completely ridiculous ending - how to retry a case in half an hour

I'm sick to death of seeing totally daft situations like this, where a couple of people suddenly start 'solving' a case in a few minutes, when someone has been locked up for nigh on 20 years and not a word has been spoken. We discover that Marlene was never called as a witness, that a second stabber came along and saw off the sleazebag - and the police allegedly did nothing and just went with the stories of two over-sexed silly little girls? Shows like this (and Broadchurch, a particularly bad offender) make the police look like a bunch of idiots, whereas the writers are actually demonstrating an utter lack of knowledge of police procedure and law. They must think we're ALL idiots. (I realised I actually was an idiot for bothering to see all three episodes of this sorry bilge full of highly unattractive characters leading completely unrealistic lives, considering their circumstances. Yes, it's even more like Broadchurch than I realised!)

PS. Please don't repeat that "it's not like the book", which is all very well but doesn't help those of us who haven't read it. However I do sympathise and also wonder why a novel that clearly worked got mangled into a drama that didn't - why do they do that? (For books that have been unrecognisably altered for the screen, I give you George Gently - so different, that all that's left is his name!)