Serrano-Mercado v. United States

Issue: (1) Whether a district court commits plain error by enhancing a sentence based on a divisible statute without requiring the government to meet its burden of proving that the conviction arose under a qualifying prong of that statute, as five circuits have held, or whether on plain-error review the burden instead shifts to the defendant to affirmatively show that the alleged predicate offense did not arise under a qualifying prong of the statute, as four circuits have held; and (2) whether the district court's additional enhancement of the petitioner's sentence based on a second predicate offense under the crime-of-violence residual clause was error in this case because that clause is unconstitutionally vague.