""You sure about that? I hardly consider getting a clearly guilty murderer found innocent "ethical""
"Ethical" in this context means honest arguments, not eliciting purjory, arguing within the reasonable bounds of the law, etc.
Prosecutors expect a fight; it's an adversary system, after all.
Ardent defense is necessary because prosecutors would otherwise routinely overstep the law and railroad people --- Delay case being but one example. They do it for self-promition, politics, you name it.
I am unsure of the "clearly guilty murderer" --- found "not guilty" (distinct from "innocent").
In such a situation --- I am told one is defending the Constitution and the People --- not the scummy criminal --- keeping the system honest.
And, no, not a lawyer. Just married one. A prosecutor.