Whether the government must prove the defendant knew the witness testified at an 'official proceeding' under 18 U.S.C. § 1513(b)(1)

QUESTION PRESENTED FOR REVIEW Whether, in a prosecution under 18 U.S.C. § 1513(b)(1), the Government must prove beyond a reasonable doubt that the defendant knew the witness against whom he allegedly retaliated gave his testimony at an “official proceeding” “before a judge or court of the United States,” as provided in 18 U.S.C. § 1515(a)(1)(A)? i