In what type of proceedings does the exclusionary rule NOT apply?

The exclusionary rule is primarily designed to deter law enforcement from violating individuals' Fourth Amendment rights against unreasonable searches and seizures in the context of criminal proceedings. It states that evidence obtained in violation of these rights cannot be used against a defendant in a criminal trial.

In civil deportation hearings, the exclusionary rule does not apply. This is because these hearings are not classified as criminal proceedings. Instead, they are administrative proceedings regarding immigration status, where different standards and rules of evidence are utilized. As a result, evidence that may have been obtained unlawfully in a criminal context might still be admissible in these civil proceedings.

The other contexts listed—criminal court trials, grand jury investigations, and preliminary hearings—are all criminal in nature, where the exclusionary rule is applicable to protect individual rights. Therefore, the correct choice highlights the specific setting where the protections offered by the exclusionary rule do not extend.