Plain procedural error in sentencing where the court bases an upward variance on extrinsic evidence first revealed at sentencing, and the deft is not given a meaningful opportunity to dispute the veracity or relevance of that evidence.
http://www.opn.ca6.uscourts.gov/opinions.pdf/18a0129p-06.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.