In a published decision, the First Circuit has determined that an inconclusive record of conviction meets an applicant's burden to prove eligibility for cancellation of removal. In so doing, the Court recognized that whether an offense poses a statutory bar is a legal question, not a factual one. The Court relied heavily on the Supreme Court's decision in Moncrieffe v. Holder.
The full text of Peralta Sauceda v. Lynch can be found here: http://media.ca1.uscourts.gov/pdf.opinions/14-2042P2-01A.pdf