Plain hearing doctrine

Definition
The plain hearing doctrine provides that

"the police may use evidence obtained in ‘plain hearing’ when they overhear speakers unrelated to the target conspiracy while listening to a valid wiretap, without having complied with the Wiretap Act requirements of probable cause and necessity as to those specific speakers. However, the agents must discontinue monitoring the wiretap once they know or reasonably should know that the phone calls only involved speakers outside the target conspiracy."