I don't think I get your argument. In a trial, unless the jury is split in which case there is either another trial or they choose not to refile, the defendant(s) is/are either found guilty or not guilty by the jury (unless I've missed out on something big). I'm not talking about not guilty because its not beyond reasonable doubt or not guilty be reason of mental defect or whatever, because at the end of the day those are both just not guilty. Maybe in the minds of the jury or in public opinion it is not black and white, but ultimately the verdict is black and white, guilty or not guilty, or they try again, right? Its like soccer, if the ball crosses the line there may be thousands of different opinions but ultimately it only matters if the referee (the jury) decides it did or did not cross the line (guilty or not guilty). I'm no lawyer or law student and I don't even have any lawyers in my family except one uncle who does tax law I think, but to me it still seems very black and white.
Most convictions are obtained on circumstantial, rather than direct evidence. Consequently there is
usually some element of doubt as to whether a person is really guilty. That doubt, however you want to quantify it, is closer to a "shade of gray" than black and white. Unfortunately the law has to establish a threshold or cut off, the compromise settled on in the American system is "guilt beyond reasonable doubt."
Don't believe me about guilt not being black and white? Look a the reactions to the Casey Anthony and OJ cases... some people believe they were innocent, some believe they were guilty. For both defendants, they just happened to have more people who didn't necessarily believe either was innocent, but who didn't think they were guilty beyond reasonable doubt. I also once served on a jury where it was clear as day that the defendant was guilty, but two jurors were sympathetic to him so they held out for acquittal.... resulting in a mistrial. I'm not sure if he was re-tried or not, but he never served any time. Does that make him innocent? Hardly.The flip side are cases where defendants are wrongly convicted due to error or misconduct... not only in the US, but elsewhere as well, to cite
one famous example. Don't get "the verdict" and "guilt" confused, the verdict might be black and white, guilt, not so much.
But all of that is an aside... we're talking sentencing and the propriety thereof.