I look at "12 Angry Men" for stuff like this.
Never once, in the end, they say the young boy was guilty of the murder or not guilty. They simply looked at the facts and collectively agreed they all had reasonable doubt with what was presented to them. They very well let a guilty boy free, but they did due process and found that the evidence provided wasn't conclusive enough for a guilty verdict. No guilty verdict "unless absolutely sure".
It's very possible Williams committed the murder. Or had a hand in it. Or didn't do it at all. We don't know. It looked conclusive, until it wasn't. There was evidence to the contrary, so in due law, Williams should've had a stay of execution. Point blank, Missouri wanted to kill a black man. And they did. And they'll get away with it. For how disappointing this is for Williams who was never given his rights for this, this disregard of the law will continue in Missouri. Perhaps Iowa next.