The landmark US Supreme Court decision that created a three-part test for determining if government action violates the Establishment Clause of the First Amendment is Lemon v. Kurtzman (1971).
The three-part test established by Lemon v. Kurtzman is known as the Lemon test. Here is a breakdown of the three parts of the Lemon test:
1. The government action must have a secular (non-religious) purpose.
2. The primary effect of the government action must neither advance nor inhibit religion.
3. The government action must not result in excessive entanglement between government and religion.
This test serves as a guideline for determining whether a particular government action complies with the Establishment Clause of the First Amendment, which prohibits the government from establishing an official religion or favoring one religion over others.
