Exclusionary Rule

The exclusionary rule states the courts will exclude any evidence that was illegally obtained, even though it may be relevant and material. Why was the exclusionary rule enacted? Why does it benefit society? Discuss in detail the Landmark Cases relating to the Exclusionary Rule, including the Fruit of Poisoned Tree Doctrine [Silverthorne Lumber Co. V. U.S. (1918)], and discuss in details the three exceptions to the Exclusionary Rule. Support your answer with direct evidence from the text and other sources.