Matter of Giraldo-Valencia, 10 Immig.Rptr. B1-132 (BIA Index Decision, October 22, 1992) (federal conviction of misprision of felony under 18 U.S.C. 4 constitutes a crime involving moral turpitude for purposes of triggering deportation, because, unlike the common law crime, a federal conviction for misprision of felony requires proof that the defendant took an affirmative step to conceal commission of a felony).