Collateral order doctrine
Collateral order doctrine is an exception in federal courts to the general rule that only final judgments are appealable. In other words, collateral order doctrine permits appeal of certain non-final judgments under the final judgment rule of 28 U.S.C. section 1291.
This doctrine has application only when:
- "those district court decisions  that are conclusive,  that resolve important questions completely separate from the merits, and  that would render such important questions effectively unreviewable on appeal from final judgment in the underlying action." This known as the "Cohen requirements," named after the decision that set the precedent.
In cases concerning defenses of immunity, immediate appeals are allowed from orders denying the immunity defense on the grounds of absolute immunity, qualified immunity, presidential immunity and double jeopardy.
More specifically, an appeal is allowed immediately from a denial of a defense in these situations:
- a defense of double jeopardy
- a governmental official's qualified immunity
- state sovereign immunity under the Eleventh Amendment
- presidential absolute immunity
- intra-military immunity under the doctrine of Feres v. U.S., 340 U.S. 135 (1950)
- foreign sovereign immunity under the Foreign Sovereign Immunities Act, 28 U.S.C. sections 1602-1611
- Guam's sovereign immunity
The U.S. Supreme Court has rejected any attempt to generalize from the above cases to a rule permitting immediate appeal whenever the district court denied an asserted right to avoid the burdens of trial. Instead, the Court has emphasized that "it is not mere avoidance of a trial, but avoidance of a trial that would imperil a substantial public interest, that counts when asking whether an order is 'effectively' unreviewable" after trial.
Another court has distilled the test to a four-part test:
- is the trial court's order tentative;
- is it capable of review without extensive examination of the merits;
- does it raise issues which could not be effectively reviewed later; and
- does it present important, unresolved legal questions for consideration by the appellate court.
In re Gen. Motors Corp. Engine Interchange Litig., 594 F.2d 1106 (7th Cir. 1979) (allowing an appeal under collateral order doctrine).
- See Digital Equipment, 114 S.Ct. at 1995-96 (the 'Cohen requirements').
- Digital Equipment Corp. v. Desktop Direct, Inc., 114 S.Ct. 1992, 1995-96 (1994).
- Cohen v. Beneficial Loan Corp., 337 U.S. 541, 546 (1949).
- Abney v. U.S., 431 U.S. 651 (1977).
- Mitchell v. Forsyth, 472 U.S. 511 (1985).
- Puerto Rico Aquaduct & Sewer Auth. v. Metcalf and Eddy, 113 S.Ct. 684, 688 (1993).
- Nixon v. Fitzgerald, 457 U.S. 731 (1982).
- Lutz v. Secretary of the Air Force, 944 F.2d 1477 (9th Cir.'91).
- Compania Mexicana de Aviacion, S.A. v. United States Dist. Ct., 859 F.2d 1354, 356 (9th Cir. 1988).
- Marx v. Guam, 866 F.2d 294, 296 (9th Cir. 1989).
- Will v. Hallock, 126 S. Ct. 952, 959 (2006).