http://www.bbc.co.uk/news/uk-25546086

"Prosecution not in the public interest"

The CPS and police are fond of that one as it is.

They really need to come clean over these. The criteria need to be clear so that public faith is restored.

The basic problem they've got is the public see prosecuting criminals as always being in the public interest. There's a certain basic logic to that. The default position of 'only prosecute if you think you can win', while equally logical, is directly at odds with the way the public want the CPS to act.

It could also be down to shoddy police work. If they were to be honest and say with the evidence we have now we do not think we can win then that might actually get some more witnesses to come forwards. Though not actually proceeding with an un-winnable case will mean that they could in theory be charged in future and so justice might merely be delayed.