Jury deadlocks in murder trial; prosecutors failed to establish defendant pulled the trigger; a state court judge dismisses the case “without prejudice.” Prosecutors retry it, get a conviction. The defendant files a habeas petition in federal court: The conviction violates the Double Jeopardy Clause. While that petition is pending, a state court vacates the conviction. (Prosecutors withheld exculpatory evidence.) The defendant remains in custody, awaiting another retrial. Ninth Circuit: His federal habeas petition is not moot, even though the conviction it challenges is no more. On remand, he can convert it to a petition challenging his detention.