A sentencing judge's misunderstanding that a defendant was buying and selling drugs from third parties, when the agreed facts showed the defendant grew the drugs himself, is a material error of fact that vitiates the sentencing discretion, because it leads the judge to treat the defendant's criminal culpability as more serious than it was. The distinction between growing cannabis for personal use (with some used to discharge a debt) and obtaining cannabis from third parties for on-selling is material to sentencing.
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