A collateral order is not final in the traditional sense, but conclusively resolves an important issue separate from the merits, and is effectively unreviewable on appeal. Collateral order appeals are permitted only in exceptional circumstances, including when double jeopardy may be at issue. The Court adopted a test used by most of the other circuits to determine whether double jeopardy is sufficiently implicated to permit collateral order review: would the claim, if successful, require dismissal of – at a minimum – an entire count?
Here, the defendants were acquitted of several substantive counts predicated on a mailing or email relating to a particular transaction. They argued that the jury necessarily decided that they lacked criminal intent as to those transactions. Thus, they argued, the government should be precluded from presenting any evidence of those transactions at trial. They conceded, however, that this would not prevent the government from presenting other evidence of criminal intent on the remaining counts, and that even if they prevailed in precluding the specified evidence, no count of the indictment would be dismissed. Thus, the Court concluded, it lacked jurisdiction. (In the process, it rejected an argument that United States v. Serafini, 167 F.3d 812 (3d Cir. 1999), which permits the government to seek review of orders of dismissal excising portions of counts, authorized review here, distinguishing the statutory provision – 18 U.S.C. § 3731 -- at issue.)
The Court held that the constructive amendment aspect of the motion was not appealable either, because constructive amendment, if it occurs, may be addressed on appeal after trial.
Finally, the Court refused to grant mandamus relief, because it identified no irreparable harm.