So, your position is that when the police arrive and see the body killed by a bullet from the killer's gun, all the killer has to do is say "it was self defense" and that's it, they have to accept it unless they can find proof that it wasn't. You allow that the killer can wait to see what evidence the prosecution can dig up before he has to come up with an explanation for any damaging evidence. This may in fact be what Florida has created in their statutes. I happen to think that there ought to be some burden to disclose the truth of what happened when you have silenced the only voice that might have been able to contradict you.
I think what you've described here is a combination of "innocent until proven guilty" and the right to confront your accusers with a hint of the protection against being forced to testify against yourself. These are foundational in the criminal justice system of the US.
