Now we have a Police Officer charged with misconduct in a Public Office:-

http://www.bbc.co.uk/news/uk-politics-25101706

As to the possibility of other officers and charges, the wording is significant.

It says "Insufficient evidence". Now that means that the DPP thinks that there is insufficient evidence to charge anyone and have a realistic chance of sustaining a sucessful prosecution.

What that also means is that there WAS some evidence but not enough. Had there been NO evidence, the words chosen would have been exactly that, there's NO evidence.