The doctrine of qualified immunity is a judicially created affirmative defense which protects public officials from being tried for violations of constitutional rights. This defense to liability for constitutional claims operates in a similar manner as the discretionary function exception to tort liability. Qualified immunity applies to federal, state, and local officials equally. Butz v. Economou, 438 U.S. 478 (1978). This immunity is designed to be immunity from suit, not merely from a finding of liability. Mitchell v. Forsyth, 472 U.S. 511 (1985). The distinction is important because qualified immunity can be invoked and the lawsuit dismissed on summary judgment without the suit going through pretrial procedure and discovery. A pretrial motion is the vehicle for invoking qualified immunity. If the lower court denies qualified immunity, a defendant may appeal that ruling before litigation on the merits proceeds. This allowance for interlocutory appeal may significantly delay the litigation.