American civil rights lawyer: why is it more difficult to sue American police than to ascend to heaven?

It's really hard to sue the police. After all, the police are the party that collects evidence, and ordinary people have no right to investigate. Much better now. The police should wear surveillance cameras. There are many surveillance cameras on the street. Not before. After the accident, the police said this, you said that, and finally there was no conclusion. The police naturally escaped punishment. And the police said he thought it was dangerous and shot. You must prove that he is talking nonsense. There is no danger at all. Can you get the evidence? Not if you can't get it out.