What is the current state of the law on sentencing based on the history and characteristics of a defendant?

18 U.S.C. 3553(a). See , e.g. , 3553(a)(1) (instructing sentencing courts to consider "the history and characteristics of the defendant"); 3553(a)(2)(C) (instructing sentencing courts to consider the need for the sentence "to protect the public from further crimes of the defendant"). But the defendant, the public, and appellate courts should not be required to engage in guesswork about the rationale for a particular sentence. Rita v. United States , 551 U.S. 338, 356, 127 S.Ct. 2456, 168 L.Ed.2d 203 (2007).