A sentencing scheme relying in part on questions decided as a matter of law by the judge violates the right to a trial by jury; where the scheme sets a mandatory minimum beneath a fixed statutory maximum, the system is sufficiently determinate to be subject to Sixth Amendment scrutiny.
http://www.opn.ca6.uscourts.gov/opinions.pdf/18a0188p-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.