What gives you the right to kill someone without a fair trail?

Even during fair trails, 10% of the people who get put to death sentence are innocent.

Imagine how many innocent people die in a war.

It doesn't mean because it's a primal instinct you can go around killing everyone.. please.

It's like claiming. Fucking is a primal instinct. So you have the right to go and rape everyone you think deserves to be raped?