[Studio25]

By the same token, the police and CPS prosecute cases where they feel they have a reasonable chance of conviction and (for cases like this) it is in the public interest.

They will interview everyone involved and decide whether they have a case. It is not up to them to decide whether or not he is guilty. Witnesses will not face the same level of "interrogation" from the police as they will from defence lawyers, so they are less likely to find weakness or contradictions in such evidence.