What circumstantial evidence is sufficient to uphold an obstruction of justice charge?

While it is true that no explicit reference to the pending grand jury investigation was made during the taped conversations, ¹⁰ we have previously held that circumstantial evidence is sufficient to uphold an obstruction of justice charge. United States v. Bufalino, 285 F.2d 408 (2d Cir. 1960). Here the evidence showed that defendants arranged the meeting, took the active role in fabricating a story about the two horses, and knew that a federal grand jury was investigating the ownership of the horses. Since the evidence established motives for the defendants to concoct the cover story, the jury could properly infer that defendants' object was to obstruct the grand jury proceedings in violation of 18 U.S.C. 1503. ¹¹