The Supreme Court holds that the Superior Court violated 14 V.I.C. § 4 when it invoked that statute to hold a bench trial on a charge of driving under the influence in violation of 20 V.I.C. § 493(b)(1) because section 493(b)(1) mandates that a convicted defendant be fined not less than $500 and section 4, by its own terms, states that it cannot be applied to cases where a mandatory sentence is imposed. The Court further holds that the Superior Court violated the appellant's Sixth Amendment right to a jury trial-which applies to the Virgin Islands pursuant to section 3 of the Revised Organic Act-when it invoked 14 V.I.C. § 4 to hold a bench trial on charges of driving under the influence and negligent driving because these offenses, which carry maximum authorized sentences greater than six months incarceration, are serious rather than petty. Finally, the Court holds that the appellant forfeited rather than waived his right to a jury trial, and that the Superior Court's violations of both 14 V.I.C. § 4 and section 3 of the ROA constitute plain errors that warrant a new trial.