Whether a § 2255 defendant may prove that his ACCA-enhanced or § 3559(c)-enhanced sentence was based on the now-unconstitutional residual clause through a process of elimination, including by surveying post-sentencing case law

QUESTION PRESENTED In Johnson v. United States, this Court held that the residual clause of the Armed Career Criminal Act is unconstitutional. In Welch v. United States, this Court applied the Johnson rule retroactively to cases on collateral review. Under 28 U.S.C. § 2255, when a defendant collaterally attacks his sentence under Johnson, he bears the burden of proving that the sentence was based upon the now-forbidden residual clause. But how may he meet that burden? May a § 2255 defendant, faced with a silent record below, prove that his ACCA-enhanced sentence (or, like Mr. Watson here, his § 3559(c)-enhanced life sentence) was indeed based upon the residual clause through a process of elimination or, put another way, may he show that a predicate offense does not fit within the recidivist statute’s alternative sources: the elements and enumerated crimes clauses? And may he prove his point by surveying postsentencing case law, including this Court’s decisions clarifying the meaning of those alternative clauses?