Final answer:
The Supreme Court case that established the "clear and present danger" doctrine for limiting freedom of expression was Schenck v. United States (1919). This decision upheld limits on speech that poses a direct threat to national security, particularly during wartime.
Step-by-step explanation:
The Supreme Court case that established the doctrine of "clear and present danger" when limiting freedom of expression was Schenck v. United States (1919). In this landmark decision, the Supreme Court upheld the Espionage and Sedition Acts, finding Charles Schenck's actions in distributing literature encouraging men to resist the draft during World War I to be a clear and present danger. This principle meant that the First Amendment's guarantee of freedom of speech has limits, particularly when such speech poses a direct threat to the United States' security or its people.
Justice Oliver Wendell Holmes, writing for a unanimous Court, eloquently expressed the view that the character and protection of an act of expression depend on the circumstances. During wartime, utterances that may be considered tolerable in peacetime can be subject to punishment.