I speak from personal experience, I was acquitted in a trial for something I did not do, on the say so of one person I was arrested and processed. I know I was innocent and I spent the best part of a year going through the mill. The Police had no case, just some very iffy hearsay. The CPS proceeded with the prosecution regardless. You see I was committing the worst possible crime, I'm a white middle class man. The accuser was an asian man. I was found not guilty very quickly, the magistarates berated the Police and the prosecution for bringing the case. All I had to do was tell the truth, I had faith in justice at the time and it was delivered. Belive me the Police and CPS are the last people to determine guilt. What we have is far from perfect but it's the best system ever devised.