Final answer:
Evidence that is illegally collected in a criminal case may be declared inadmissible under the exclusionary rule. This rule was established and applied in landmark cases such as Mapp v. Ohio and Weeks v. United States, reinforcing that both direct and derivative evidence obtained illegally are not permissible in court.
Step-by-step explanation:
The evidence that is illegally collected in a criminal case and may be declared inadmissible is covered under the exclusionary rule. In significant cases such as Mapp v. Ohio and Weeks v. United States, the Supreme Court established that evidence obtained without proper legal authority, for example, without a search warrant or not fitting an exception to the warrant requirement, cannot be used in state or federal criminal trials. This follows the principle known as the "fruit of the poisonous tree," highlighting that not only is the directly gained illegal evidence inadmissible but also any further evidence that stemmed from the initial illegal search or seizure.
Despite its stringent application, the exclusionary rule does have exceptions, such as the "good faith" exception and "inevitable discovery" exception, which allow evidence in specific circumstances where the violation of procedure does not warrant suppression.