In convicting an accused, the jury may have only had to determine a narrow range of facts; circumstances relevant to the offending but not being elements of the offence do not need to be proved to the jury’s satisfaction to the standard of beyond reasonable doubt. They do, however, need to be proved to the sentencing judge’s satisfaction to that standard. Should the offender have the right to have the jury make that decision?
Normally sentencing judges, when faced with an issue of fact outside the facts implicit in a jury’s verdict, make their own findings to the appropriate standard of proof. The questions set out above only arise when the judge is bound by mandatory sentencing guidelines. Mandatory guidelines (a slightly oxymoronic expression) are like the elements of an offence: a fact has a necessary consequence. That, essentially (my analysis is expressed differently from the Court’s), is the reason the Supreme Court of the United States held unconstitutional the provision that made the Federal Sentencing Guidelines mandatory in United States v Booker  USSC No 04-104, 12 January 2005.
In New Zealand we await the introduction of sentencing guidelines which are being prepared by our newly created Sentencing Council. These guidelines will not be mandatory: s 21A of the Sentencing Act 2002 (inserted by an amendment in 2007, not yet available online as not yet in force; oops, yes it is online - thanks to Ben Hamlin for pointing this out - here: s 21A) will require the guidelines to be adhered to unless the Court is satisfied that adhering to them would be contrary to the interests of justice. This seems to mean that, say, an aggravating fact found by the sentencing judge to be proved beyond reasonable doubt, will only have the consequence indicated in the guidelines if the offender does not satisfy the judge that it would be contrary to the interests of justice to impose that consequence. But more generally, either side may seek to move the court away from the guideline consequence.
Once the guidelines are subject to departure, will notice be required of an intention to seek departure? If notice might be appropriate, should it always be given, or should it only be required when a sought departure is of a high level? In Irizarry v United States  USSC No 06-7517 (12 June 2008) it was held that, now that the guidelines are no longer mandatory, notice is not required because the guidelines don’t entitle either party to expect a particular outcome:
“Sound practice dictates that judges in all cases should make sure that the information provided to the parties in advance of the hearing, and in the hearing itself, has given them an adequate opportunity to confront and debate the relevant issues. We recognize that there will be some cases in which the factual basis for a particular sentence will come as a surprise to a defendant or the Government. The more appropriate response to such a problem is not to extend the reach of Rule 32(h)’s notice requirement categorically, but rather for a district judge to consider granting a continuance when a party has a legitimate basis for claiming that the surprise was prejudicial.”
(per Stevens J, delivering the opinion of the Court, slip op. p 7)
There may be times when the sentencing exercise becomes rather protracted, as issues of fact are determined and their consequences explored. It would be ludicrous to return these issues to the jury, and in a remote sense the sentencing council is a partial surrogate; Blackstone bewailed the removal of such issues from the jury, but his remarks could today be applied to the exercise of determining whether to depart from sentencing guidelines:
“[H]owever convenient these [new methods of trial] may appear at first (as doubtless all arbitrary powers, well executed, are the most convenient) yet let it be again remembered, that delays, and little inconveniences in the forms of justice, are the price that all free nations must pay for their liberty in more substantial matters; that these inroads upon this sacred bulwark of the nation are fundamentally opposite to the spirit of our constitution; and that, though begun in trifles, the precedent may gradually increase and spread, to the utter disuse of juries in questions of the most momentous concerns." 4 Commentaries on the Laws of England 343-344 (1769).” (quoted by Stevens J in US v Booker, above).
For an argument that the mandatory guidelines were not unconstitutional, see Richard Posner, “How Judges Think” (2008), at 290-292:
“Why the mandatory feature of the guidelines should have been thought to violate the Sixth Amendment, a provision designed for the protection of criminal defendants, is a mystery. Gearing sentences to findings made on the basis of evidence gave the defendants more procedural rights than they had had before the guidelines, when judges could pick any point in the statutory sentencing range when determining a sentence. Because judges' discretion had been greater (hence the greater variance in sentences), defendants' rights had been fewer, since a plea to a judge to exercise his discretion in favour of imposing a lenient sentence is a plea for mercy rather than a claim of right, unless his discretion is tightly cabined, as it was not in the pre-guidelines sentencing regime.” [p 291, Posner's emphasis]