What does the Double Jeopardy Clause of the Fifth Amendment prohibit, and what are its major exceptions?

The Double Jeopardy Clause attaches once a jury is sworn in (or when the first witness is sworn in for a bench trial) and bars successive prosecutions for the same offense after a final judgment. However, the dual sovereignty doctrine allows both the federal government and a state government to prosecute the same conduct under their respective laws (as happened in the Rodney King case, where officers acquitted in state court were later convicted in federal court). A mistrial declared due to manifest necessity (such as a hung jury or juror misconduct) does not bar retrial. Civil lawsuits are also separate from criminal prosecution and are not barred by double jeopardy.