My best guess is that I have participated in at least three hundred criminal sentencings as either a prosecutor or as a defense attorney. [Never as a defendant....knock on wood!]
Sometimes the outcome is already known---for instance when there is a minimum mandatory sentence or when the Court has concurred in a plea bargain reached between the prosecution and the defense. Often the outcome is unknown--until the judge imposes sentence. Even then the final outcome may depend upon one or more appeals and re-sentencings.
I recall my first sentencing hearing before The Honorable Mark W. Bennett, United States District Judge here in the Northern District of Iowa. Judge Bennett wrote an article for "The Champion" magazine last year. ("Heartstrings or Heartburn: A Federal Judge's Musings On Defendants' Right and Rite of Allocution" (March 2011)). Judge Bennett has sentenced over 2500 criminal defendants in federal court. My first sentencing before His Honor was about ten years' ago, at a time when the federal sentencing guidelines were rigidly applied. After calculating the guideline range (I think it was 57 to 71 months in prison) Judge Bennett said "Mr. Greer, I am inclined to sentence your client to the lower end of the guidelines unless you want to try and talk me out of it." I think "No thank you, Your Honor" was all I said that day.
Federal sentencing guidelines are no longer mandatory. Effective advocacy at sentencing is crucial. And a defendant's allocution is more important than ever. Allocution is the procedure during sentencing when a judge gives a convicted defendant the opportunity to make a personal statement on his own behalf to mitigate the punishment that is about to be imposed. The defendant does not have to be sworn before he makes his address, his comments are not subject to cross-examination, and the opportunity may include the right to offer evidence (such as an explanation for his conduct or a reason why severe sentence should not be imposed) beyond a request for mercy or an apology for his conduct.
Sentencings go better for defendants who are contrite and sorry for their conduct. Defense attorneys at sentencings should be more like biographers (or mortitians), sharing their client's accomplishments lest we not forget Mark Antony's admonition that "The evil that men do lives after them; The good is oft interred with their bones". (Shakespeare's Julius Ceaser)