kek you're retarded. cops are not supposed to charge you if you acted in self defense. prosecutors are not supposed to take the charges to court. they have an ethical duty to only take to trial cases in which they believe the accused is guilty and they believe they have enough evidence to prove this beyond a reasonable doubt. this is because, apart from the cost to the taxpayer of a trial, the process is an incredible burden on the accused. lost income and employment and educational opportunities as well as reputational damage that potential does not go away even if you are aquitted, not to mention lawyers fees which can easily go into the hundreds of thousands and for which you will never be reimbursed by the state.  when prosecutors start targetting people who have not broken the law but merely engaged in a behaviour that the prosecutor does not like, this does act as a massive deterrent from that behaviour even if the prosecutor is unable to secure any conviction.
Australia