But everybody is like this to an extent, so you need to fix this in other ways too. This is why reasonable countries have a whole bunch of process around legal punishment, and don't just throw someone in prison after a police officer says so. All the restrictions on how evidence is gathered and what kind of proof needs to be provided are ways to work around this problem. The police and prosecutor might decide someone is guilty, but they still have to convince twelve ordinary people. (Or whatever the process is in your country of choice.)

It sounds like this is where things really fell apart with the postal scandal, and the courts were willing to convict with insufficient evidence.