I understand what you are saying @JoyDivision79 . But modern technology means it doesn't have to be that way. We have metadata on phones, GPS on cars, CCTV, ring doorbells and dash cams, DNA evidence.
The problem is the lack of reliable control of information. There are people in the USA who are convicted, another person confesses and is then convicted, and the original conviction is not overturned as no one realises. A good country wide IT system with AI that actively searches and filters things can help.
Also I don't believe that the police should decide who is referred to be prosecuted and what evidence the CPS should get. There should be oversight, again independent people and AI, and all evidence should be forwarded. IANAL or police and I apologise if I have misunderstood any of the legal process.