Final answer:
The exclusionary rule prohibits the use of evidence obtained through illegal searches or seizures, affecting law enforcement by limiting the evidence admissible in court. There are exceptions to this rule, including the good faith exception and the inevitable discovery doctrine.
Step-by-step explanation:
The exclusionary rule is a legal principle that prohibits the use of evidence obtained through violations of the Fourth Amendment's protections against unreasonable searches and seizures. This rule affects law enforcement by preventing evidence gathered from an illegal search or seizure to be used in a state criminal trial. The landmark case Mapp v. Ohio broadened the application of this rule to state courts, originally established at a federal level by Weeks v. United States.
There are exceptions to the exclusionary rule such as the good faith exception, where evidence may be admitted if law enforcement officers operated based on a belief that they were following legal procedures. Another exception is the inevitable discovery doctrine, which allows for the use of evidence that would have been found regardless of the illegal search or seizure.
When evidence is obtained illegally, it cannot be used in court, nor can any secondary evidence derived from the initial illegal act, often referred to as the "fruit of the poisonous tree." This reinforces the requirement that law enforcement must operate within legal boundaries to protect individual rights.